cv4pve-cli-tui/docs/plans/guest-tui-mvp.md

# Guest TUI MVP

## Problem

Manage Proxmox guests (VMs and LXC containers) from the terminal without remembering
`cv4pve-cli` syntax: list them, start/shutdown/stop/reboot, and change CPU cores,
memory and disk size.

## Approach

Thin subprocess wrapper around `cv4pve-cli` (tested against 2.4.0) plus a Textual app.
The app never handles credentials: it uses whatever context `cv4pve-cli config use`
selected.

Observed CLI behaviour the design relies on:

- `get guests -o json` -> list of dicts with `vmid`, `type` (`qemu`|`lxc`), `node`,
  `name`, `status`, `maxcpu`, `maxmem` (bytes), `maxdisk` (bytes), ...
- `show vm|ct <node> <vmid> -o json` -> list of `{"key": ..., "value": ...}`.
- `api get /nodes/<node>/<qemu|lxc>/<vmid>/pending -o json` -> list of
  `{"key", "value", "pending", "delete"}`; `pending` non-null means not yet applied.
- Async actions print a UPID and exit 0 **even when the task fails**. With `--wait`
  the CLI waits for the task and exits non-zero (5) with the error text on failure.
  Every mutating call therefore uses `--wait`.
- `do stop` refuses to run without `-y` (verified); `-y` is accepted by all four
  lifecycle actions, so it is always passed.
- Errors: non-zero exit, message on stdout/stderr. Sync failures are multi-line
  (`Error: ...` / `Call: ...` / `Alias: ...`). Success is judged by exit code only,
  never by parsing UPID text.
- Each call costs ~0.5 s (.NET startup), so calls run in worker threads.
- `get guests` (`/cluster/resources`) lags a few seconds behind actions; after an
  action the app reads the acted-on guest's live status from
  `api get /nodes/<node>/<qemu|lxc>/<vmid>/status/current` (key/value list).

### Module `cv4pve_tui/cli.py`

- `CliError(Exception)` - `str()` is the CLI's combined, stripped output;
  `.summary` is one line for the UI: the first non-empty line that is not a UPID,
  `Error:`-prefix stripped, plus the following indented detail line if the first
  line ends with `:`.
- `run(*args) -> str` - `subprocess.run(["cv4pve-cli", *args], capture_output=True,
  text=True, stdin=DEVNULL, timeout=330)`; non-zero exit -> `CliError`.
- `kind(guest) -> "vm" | "ct"` - from `type` (`qemu` -> `vm`, `lxc` -> `ct`).
- `list_guests() -> list[dict]` - sorted by `vmid`.
- `guest_config(guest) -> dict` - key/value list flattened to a dict.
- `disks(config, kind) -> dict[str, str]` - resizable disks -> size string.
  VM: `scsiN|virtioN|sataN|ideN` with a `size=`, excluding `media=cdrom` and
  cloud-init. CT: `rootfs`, `mpN`.
- `ACTIONS = ("start", "shutdown", "stop", "reboot")`;
  `action(name, guest)` -> `do <name> <kind> <node> <vmid> -y --wait`;
  unknown name -> `ValueError`.
- `set_resources(guest, cores=None, memory_mb=None)` ->
  `set <kind> config <node> <vmid> [--cores N] [--memory M] --wait`; values must be
  positive ints; nothing to set -> `ValueError`.
- `resize_disk(guest, disk, grow_gb)` -> `do resize <kind> disk <node> <vmid> <disk>
  +<grow_gb>G --wait`; `grow_gb` must be a positive int (growth only - Proxmox cannot
  shrink, and an increment cannot shrink by construction).
- `pending_keys(guest) -> list[str]` - keys with a non-null `pending`.

### Module `cv4pve_tui/app.py`

- `DataTable` of guests: VMID, name, type, node, status, cores, memory (MiB),
  disk (GiB). Cursor row = selected guest.
- Keys: `s` start, `S` shutdown, `x` stop (hard), `r` reboot, `e` edit,
  `g` refresh, `q` quit.
- `shutdown`, `stop`, `reboot` open a confirm modal naming the guest; `stop` says it
  is a hard power-off. `start` needs no confirmation.
- `e` opens an edit modal: cores, memory MiB, disk select + "grow by GiB".
  Empty field = unchanged. Disk growth gets its own confirm (irreversible).
- After `set_resources`, if `pending_keys` contains `cores` or `memory`, notify that
  the change applies at next reboot.
- All CLI calls in thread workers; results/errors via `notify` (errors show
  `CliError.summary`); table refreshes after each action.
- A "working" notice is shown when an action starts (`--wait` can block minutes),
  and a second action on a guest that is already busy is refused.
- Action keys on an empty table do nothing (no crash).

### UI contract (shared by tests and implementation)

- `app.py` does `from cv4pve_tui import cli` and always calls `cli.<function>(...)`,
  so tests monkeypatch `cv4pve_tui.cli.<function>`.
- `class GuestApp(App)`; `def main()` runs it.
- Guest table: `DataTable` with id `guests`, one row per guest, row key = str(vmid),
  in `list_guests()` order. Loaded on mount.
- `ConfirmScreen(ModalScreen[bool])`: buttons `#yes` / `#no`; its text names the guest
  (name and vmid); for `stop` it contains the words "hard power-off".
- `EditScreen(ModalScreen)`: `Input#cores`, `Input#memory`, `Select#disk`,
  `Input#grow`, buttons `#apply` / `#cancel`. Inputs are pre-filled with nothing
  (empty = unchanged); placeholders show current values. Disk options come from
  `cli.disks(cli.guest_config(guest), cli.kind(guest))`.
  On apply: if cores/memory given -> `cli.set_resources(guest, cores=..., memory_mb=...)`
  (only the given ones, as ints); if grow given -> `ConfirmScreen` first, then
  `cli.resize_disk(guest, disk, grow_gb)`. Non-integer or <= 0 input -> `notify`
  with severity "error" and no CLI call.
- Thread workers (`@work(thread=True)` or `run_worker(..., thread=True)`); tests wait
  with `await app.workers.wait_for_complete()` then `await pilot.pause()`.

## Out of scope

Create/delete, snapshots, migration, console, backup, in-app context switching,
sockets/vCPU/hotplug settings, live auto-refresh.

## Steps

- [x] Project skeleton (`uv`, `pyproject.toml`, entry point `cv4pve-tui`) -
      `uv run python -c "import cv4pve_tui"` succeeds.
- [x] Tests for `cli.py` with `subprocess.run` mocked - fail before implementation.
- [x] `cli.py` - tests pass.
- [x] Tests for the app with Textual `run_test` and `cli` functions mocked.
- [x] `app.py` - tests pass.
- [x] Read-only smoke test against the real cluster (listing, edit dialog disk options,
      pending check).
- [x] Live edit (cores/memory), shutdown, start, reboot on CT 104 (mainframe), restored
      to baseline afterwards. Disk resize not run live (irreversible).

## Open questions

None blocking.

---

# Context switching

## Problem

Several cv4pve-cli contexts (clusters) exist; switch between them inside the TUI
instead of quitting and running `cv4pve-cli config use`.

## Decision

Option A: switching runs `cv4pve-cli config use <name>`, which changes the **global**
current context (all shells and scripts follow) and stays after the app exits. cv4pve-cli
2.4.0 has no per-call context flag or env var (verified), so there is no app-local option.

Observed CLI behaviour:

- `config list` has no `-o json`. Text output, one line per context; current one
  prefixed with `* `, others with two spaces:
  `* mainframe            mainframe.iot.home.arpa:8006   (api-token)`
  `  mainframe-edge       mainframe-edge.home.arpa:8006   (api-token)`
- `config use <name>` -> exit 0 on success; unknown name -> exit 3,
  `Error: Context '<name>' not found.`, current context unchanged.

### `cli.py`

- `contexts() -> list[dict]` - `run("config", "list")`, each line parsed to
  `{"name", "host", "auth", "current": bool}` (regex
  `^(\*)?\s*(\S+)\s+(\S+)\s+\((.*)\)\s*$`); non-matching lines are ignored.
- `use_context(name)` - `run("config", "use", name)`.

### `app.py` (UI contract)

- The active context is always visible: `app.sub_title == f"context: {name}"`
  (shown in the Header). Set on mount from `cli.contexts()` and after every switch.
  If `contexts()` fails: error notify, sub_title `context: ?`.
- Key `c` opens `ContextScreen(ModalScreen[str | None])` with `OptionList#contexts`,
  one option per context, option id = context name, current one marked with `*`.
  Selecting an option dismisses with its name; `escape` dismisses with `None`.
- `c` while any guest is busy -> warning notify, no screen (VMIDs collide across
  clusters, so the busy guard would point at the wrong cluster).
- Selecting the current context or dismissing -> no CLI call.
- A reload started before a switch must not refill the table (generation counter);
  `g` and `c` are refused while a switch runs; the post-action reload finishes before
  the guest stops being busy.
- Selecting another context: table cleared immediately (old cluster's guests must not
  stay actionable), then in a worker `cli.use_context(name)`, sub_title updated, guests
  reloaded. On `CliError`: error notify with summary, sub_title re-read from
  `cli.contexts()`, guests reloaded.

## Out of scope

Adding/editing/deleting contexts, `config verify`, restoring the original context on exit.

## Steps

- [x] Tests for `contexts`/`use_context` and the UI contract above - red first.
- [x] Implementation - full suite green, ruff clean.
- [x] Live: open the list, switch to `mainframe-edge` and back to `mainframe`
      (only `config use` and read-only listing; no guest actions); final context
      is `mainframe`.
- [ ] Push `feat/guest-tui-mvp`, merge to `main` (user-approved).

---

# LXC shell

## Problem

Open an interactive shell in a running LXC container from the TUI. cv4pve-cli 2.4.0 has
no console/shell/exec for LXC (verified: no command; the Proxmox API has no LXC exec),
so the app goes around it: SSH to the PVE node as root and run `pct enter <vmid>`.

## Decision

Option 1 from the discussion: `ssh -t root@<node> pct enter <vmid>`. The node name is
the SSH host (resolves via DNS here: `mainframe`, `mainframe-edge`); the user's key is in
root's `authorized_keys` (verified: `ssh -o BatchMode=yes root@mainframe pct status 104`
-> `status: running`). This bypasses cv4pve-cli and its API token.

## `app.py` (UI contract)

- Key `t` ("Shell") on the selected guest.
- Only for `type == "lxc"` and `status == "running"`; otherwise a warning notify that
  says why (not a container / not running) and nothing runs. Empty table: nothing.
- Busy guest (action running) -> warning notify, nothing runs.
- Runs on the main thread inside `with self.suspend():` -
  `subprocess.run(["ssh", "-t", f"root@{node}", "pct", "enter", str(vmid)])`
  (no capture, no timeout: the user's terminal is handed over; `import subprocess` in
  app.py so tests patch `cv4pve_tui.app.subprocess.run`).
- Exit 255 (ssh itself failed) -> error notify naming the guest and the code. Other
  exit codes are the container shell's last status (`exit` after a failed command
  gives 1) and are not errors.
- Inside `suspend()`, right before ssh, the terminal gets a full reset (`ESC c`, what
  `reset` sends) so the container shell starts on a clean screen without leftover TUI
  terminal modes (user request). Done locally, not in the container: no dependency on
  `reset` existing there, and `pct enter` stays unchanged.
- `OSError` from `subprocess.run` is caught *inside* the `suspend()` block: Textual
  8.2.8's `suspend()` has no try/finally, so an exception escaping it leaves the app
  suspended.
- The guest table reloads after the shell returns (the user may have stopped or
  rebooted the container from inside).
- `textual.app.SuspendNotSupported` (headless / unsupported driver) and `OSError`
  (no `ssh` binary) -> error notify, app keeps running.
- Tests: `App.suspend` raises `SuspendNotSupported` under `run_test`, so tests replace
  `app.suspend` with a no-op context manager (e.g. `contextlib.nullcontext`) unless
  testing that error path.

## Out of scope

VM consoles (serial/VNC), configurable SSH user/host/options, termproxy/websocket.

## Steps

- [x] Tests for the UI contract above - red first.
- [x] Implementation - full suite green, ruff clean. README key table gets `t`.
- [x] Interactive test by the user: `t` on CT 104, `exit`, back in the table; screen
      clean after the reset.
- [ ] Push `feat/lxc-shell`, merge to `main` (user-approved).

---

# Guest info screen: backups, backup now, network (read-only) - delivery A

## Problem

Per guest, see its latest backups and network setup, and start a backup now. Network
*editing* is delivery B (separate, live-tested), not part of this.

## Decisions (user-approved)

- Backup now uses the scheduled job's settings: `--mode snapshot --compress zstd`.
  Storage is chosen from the node's backup-capable storages, preselected to the job's
  storage (`truenas-backup` here), `local` as alternative.
- Manual backups get `--notes-template "{{guestname}} (manual)"` so they are
  recognisable. Note for the user: `truenas-backup` has storage prune `keep-all=1`, but
  the job has `keep-last 3` per guest; a manual backup there likely counts towards it at
  the job's next run (not verified).

Observed CLI behaviour (cv4pve-cli 2.4.0, all read-only probes):

- `get node storages <node> -o json` -> list of dicts: `storage`, `content`
  (comma list, e.g. `iso,snippets,import,backup,vztmpl`), `enabled`, `active`, `type`,
  `avail` (bytes).
- `get cluster backup-jobs -o json` -> list of dicts: `id`, `enabled`, `storage`,
  `schedule` (e.g. `mon,wed,fri 04:00`), `mode`, `compress`, `all` (1 = all guests),
  `vmid` (comma list or null), `exclude` (comma list or null), `node` (null = all),
  `next-run` (epoch), `prune-backups` (e.g. `{"keep-last":"3"}`).
- `get guest backups <node> <storage> <vmid> -o json` -> list of dicts: `volid`
  (`truenas-backup:backup/vzdump-lxc-104-2026_11_02-04_11_47.tar.zst`), `ctime` (epoch),
  `size` (bytes), `format`, `notes`, `protected`, `subtype` (`lxc`|`qemu`), `vmid`.
- `do backup guest <node> <vmid> <storage> [--key value]` - no `--yes` option.
  vzdump params: `mode` snapshot|suspend|stop, `compress` 0|1|gzip|lzo|zstd,
  `notes-template`.
- CT net config: `netN` = `name=eth0,bridge=vmbr0,hwaddr=BC:24:11:36:DE:78,ip=dhcp,ip6=auto,type=veth`
  (optional `gw`, `gw6`, `tag`, `firewall`, `rate`, `mtu`, ...).
- VM net config: `netN` = `virtio=02:24:A6:49:A8:25,bridge=vmbr0[,tag=..][,firewall=1]`
  (first item is `<model>=<MAC>`); IP settings live in `ipconfigN` (cloud-init), e.g.
  `ip=dhcp`.
- Runtime IPs, CT (running): `get ct interfaces <node> <vmid> -o json` -> list of
  dicts: `name`, `hwaddr`, `inet` (e.g. `172.16.41.200/23`), `inet6` (may be absent/
  null), `ip-addresses` (JSON string).
- Runtime IPs, VM (running, guest agent): `get vm agent network <node> <vmid> -o json`
  -> `[{"key": "result", "value": "<JSON string>"}]`; the JSON is a list of
  `{"name", "hardware-address", "ip-addresses": [{"ip-address", "prefix",
  "ip-address-type": "ipv4"|"ipv6"}]}`. Fails when the agent is not running.

### `cli.py`

- `backup_storages(guest) -> list[str]` - storages on the guest's node whose `content`
  contains `backup` and that are enabled and active, in API order.
- `backup_jobs() -> list[dict]`.
- `job_storage(jobs, guest) -> str | None` - storage of the first enabled job covering
  the guest: (`all` truthy and vmid not in `exclude`) or vmid in `vmid`; and `node` null
  or equal to the guest's node.
- `backup_jobs()` parses `prune-backups` when the CLI returns it as a JSON string
  (real output: `'{"keep-last":"3"}'`).
- `backups(guest, storages) -> list[dict]` - all backups of the guest on those
  storages, newest first (`ctime` desc). Each dict gets `storage` (from volid prefix).
- `backup_now(guest, storage)` -> `do backup guest <node> <vmid> <storage> --mode
  snapshot --compress zstd --notes-template "{{guestname}} (manual)" --wait`.
- `parse_net(value: str) -> dict` - `netN` string to an ordered dict of key -> value
  (insertion order kept, so B can re-serialise unchanged keys). VM: the first
  `<model>=<MAC>` item is kept as is (key = model).
- `nets(config) -> dict[str, dict]` - `netN` keys (sorted by N) -> `parse_net(value)`.
- `interfaces(guest) -> list[dict]` - runtime interfaces as
  `{"name", "mac", "ipv4": [cidr...], "ipv6": [cidr...]}`, loopback (`lo`) excluded.
  CT via `get ct interfaces` (addresses from its `ip-addresses` JSON string - `inet6`
  alone holds only one, e.g. link-local, and misses the global SLAAC address), VM via
  `get vm agent network`. Only called when the guest's live status is running.

### `app.py` (UI contract)

- Key `i` on a guest opens `InfoScreen(guest)` (a `Screen` or `ModalScreen`). Empty
  table: nothing.
- InfoScreen loads in a thread worker: config -> `cli.nets`, `cli.interfaces` (only if
  status is `running`; a failure there is shown inline as "unavailable: <summary>", not
  as a fatal error), `cli.backup_storages`, `cli.backup_jobs`, `cli.backups`.
- Shows:
  - `DataTable#backups`: Date (local time, `YYYY-MM-DD HH:MM`), Storage, Size (GiB, one
    decimal), Format, Notes. Newest first. A `Static#jobs` line naming the job(s) that
    cover the guest (schedule, storage, `keep-last` if present) or "No backup job
    covers this guest".
  - `DataTable#nets`: Iface (net0...), Bridge, VLAN (`tag` or `-`), MAC, IPv4 (CT `ip`,
    VM `ipconfigN` `ip`, or `-`), IPv6 (CT `ip6`, VM `ipconfigN` `ip6`, or `-`),
    Firewall (`yes`/`no`).
  - `DataTable#addresses`: Interface, MAC, IPv4, IPv6 (runtime), or the unavailable
    line.
- VMIDs are reused: a deleted guest's backups keep the VMID and are listed by the API
  for the new guest. Backups whose notes (the job's `{{guestname}}`) are non-empty and
  are neither the current name nor start with `<name> ` (e.g. `debian (manual)`) are
  hidden by default; `Static#hidden` says how many; key `a` toggles showing them,
  marked `(earlier guest)`. Backups without notes are always shown.
- Key `b` in InfoScreen: `BackupScreen` modal with `Select#storage` (options =
  backup storages, preselected `job_storage` or the first), text saying mode snapshot,
  zstd, and the guest; buttons `#yes` / `#no`; escape = no. On yes: guest marked busy
  in `app.busy` (refuse with a warning if already busy), "backup started" notify, worker
  runs `cli.backup_now`, then "backup done"/error notify, busy released, backup list
  reloaded if the InfoScreen is still open.
- `escape` closes InfoScreen; `g` in InfoScreen reloads it.
- Every CLI failure -> error notify with `_message(exc)`, app keeps running.

## Steps

- [x] Tests (cli + UI contract) - red first.
- [x] Implementation - suite green, ruff clean, README keys `i` / `b`.
- [x] Read-only live check: open InfoScreen for CT 104 and VM 108, data shown.
- [x] User tests "Backup now" on CT 104 (`debian (manual)`, 2026-11-02 21:09).
- [ ] Push `feat/guest-info`, merge to `main` (user-approved after the test).

---

# Network editing - delivery B

## Problem

Change a guest's network settings from the info screen: bridge, VLAN, firewall, IPv4
and IPv6 (incl. SLAAC), without breaking what is not edited.

## Decisions (user-approved)

- VM IP settings go through cloud-init `ipconfigN`, only when the VM has a cloud-init
  drive; they apply at the next boot. VMs without cloud-init: IP fields disabled with a
  note (IP is configured inside the VM).
- IPv4 modes: DHCP / Static (CIDR + optional gateway) / None.
  IPv6 modes: SLAAC / DHCP / Static (CIDR + optional gateway) / None.
- Undo key `u`: restores the values from before the last network change made in this
  app session for that guest.
- Out of scope: adding/removing interfaces, MAC, mtu, rate, trunks, DNS.

API facts (Proxmox VE 9.2, `api usage ... config set -v`):

- LXC `net[n]`: `name=<string>[,bridge][,firewall=<1|0>][,gw=<IPv4>][,gw6=<IPv6>]
  [,host-managed][,hwaddr][,ip=<IPv4/CIDR|dhcp|manual>][,ip6=<IPv6/CIDR|auto|dhcp|manual>]
  [,link_down][,mtu][,rate][,tag=<int>][,trunks][,type=veth]`. `ip6=auto` = SLAAC.
  Applied immediately on a running CT.
- VM `net[n]`: `[model=]<enum>[,bridge][,firewall=<1|0>][,link_down][,macaddr][,mtu]
  [,queues][,rate][,tag=<int>][,trunks][,<model>=<macaddr>]`. Applied immediately.
- VM `ipconfig[n]`: `[gw=<IPv4>][,gw6=<IPv6>][,ip=<IPv4/CIDR|dhcp>][,ip6=<IPv6/CIDR|dhcp|auto>]`
  (cloud-init; "no explicit gateway with dhcp"). Applies at the next boot.
- `delete=<list>` removes settings (used when `ipconfigN` ends up empty).
- `get node network <node> -o json` -> list of dicts with `iface`, `type`
  (`bridge`, `OVSBridge`, `eth`, ...), `active`.
- Cloud-init drive: a disk value containing `cloudinit`
  (`ide2 = local-lvm:vm-108-cloudinit,media=cdrom`).

### `cli.py`

- `bridges(guest) -> list[str]` - `iface` of entries with type `bridge` or `OVSBridge`
  on the guest's node, sorted.
- `format_net(d: dict) -> str` - inverse of `parse_net`: `k=v` joined by `,`, order
  kept. `format_net(parse_net(s)) == s` for the real samples.
- `has_cloudinit(config) -> bool`.
- `apply_link(net, bridge, tag, firewall) -> dict` - a copy of `net`: `bridge` set;
  `tag` int 1-4094 or None (None removes `tag`); `firewall` True -> `"1"`, False ->
  `firewall` removed. Existing keys keep their position; new keys are appended.
- `ip_mode(cfg, family) -> tuple[str, str, str]` - `(mode, cidr, gw)` read from a
  parsed LXC net or VM ipconfig dict; family 4 uses `ip`/`gw`, 6 uses `ip6`/`gw6`.
  Modes: `dhcp`, `static`, `none`, and for 6 also `auto`; `manual` reads as `none`.
- `apply_ip(cfg, family, mode, cidr="", gw="") -> dict` - copy with the family's keys
  set: `dhcp`/`auto` -> `ip[6]=dhcp|auto`, gateway removed; `static` -> `ip[6]=<cidr>`,
  `gw[6]` set if given else removed; `none` -> both removed. Validation (ValueError):
  static needs a CIDR of the right family with a `/prefix`
  (`ipaddress.ip_interface`); a gateway must be an address of the same family; `auto`
  only for family 6.
- `set_net(guest, changes: dict[str, str | None])` -> one call:
  `set <kind> config <node> <vmid> [--<key> <value> ...] [--delete <k1,k2>] --wait`;
  `None` values go to `--delete`. Empty `changes` -> ValueError.

### `app.py` (UI contract)

- Key `n` in InfoScreen opens `NetScreen` for the guest (needs the loaded config;
  nothing if the guest has no `netN`).
- `NetScreen(ModalScreen)`: `Select#iface` (netN keys), `Select#bridge`
  (`cli.bridges`), `Input#tag` (empty = none), `Checkbox#firewall`, `Select#ipv4`
  (`dhcp`/`static`/`none`), `Input#ipv4_cidr`, `Input#ipv4_gw`, `Select#ipv6`
  (`auto` labelled SLAAC / `dhcp` / `static` / `none`), `Input#ipv6_cidr`,
  `Input#ipv6_gw`, buttons `#apply` / `#cancel`; escape = cancel. Prefilled from the
  current values of the selected interface; changing `#iface` prefills again.
  VM without cloud-init: IP widgets disabled and `Static#ip_note` explains why.
- Apply: build the new netN (and for VMs the new ipconfigN) with `apply_link` /
  `apply_ip`; ValueError -> error notify, screen stays open, no CLI call. No change ->
  info notify, nothing else. Otherwise `ConfirmScreen` listing each changed key with
  its old and new value (raw strings); for a running guest it says link changes apply
  immediately, and for VM ipconfig that it applies at next boot.
- On yes: guest busy (refuse if busy), worker runs `cli.set_net(guest, changes)`,
  done/error notify, busy released, InfoScreen reloads. On success the old values
  (`None` for keys that did not exist) are stored as the guest's undo entry.
- Live finding (CT 104): Proxmox applies a changed `ip` on a running CT, but static ->
  dhcp left the CT without IPv4 (no DHCP client restart) until the CT was rebooted.
  The confirm therefore says, for IP changes on a running container, that a reboot of
  the container may be needed. Proxmox re-orders keys when it stores `netN`.
- Review fixes: undo entries are cleared on a context switch (VMIDs repeat across
  clusters); `has_cloudinit` only looks at disk keys; CIDR needs a decimal prefix
  1-32 / 1-128 (no netmask form, no /0); fields the user did not touch are not rewritten
  (e.g. `ip6=manual` stays).
- Key `u` in InfoScreen: no undo entry -> info notify. Otherwise `ConfirmScreen`
  showing what will be restored, then `cli.set_net(guest, old_values)` the same way;
  the undo entry is cleared after success.

## Steps

- [x] Tests - red first.
- [x] Implementation - suite green, ruff clean, README keys `n` / `u`.
- [x] Live on CT 104 (approved), each step reverted: firewall off->on->off; VLAN
      none->99->none (undo key); IPv6 SLAAC->DHCP->SLAAC; IPv4 DHCP->static
      172.16.41.200/23 gw 172.16.40.1->DHCP. Bridge change cannot be tested live: the
      node has a single bridge (`vmbr0`). Final net0 string identical to the baseline.
- [ ] Push `feat/network-edit`, merge to `main` (ask first).