Add snapshots to the info screen: take, roll back, delete

A "Snapshots" section on the info screen lists the snapshots, newest
first, without Proxmox's "current" pseudo entry. Keys:

- p takes a snapshot. The name defaults to tui_YYYYMMDD_HHMM, the
  description is optional, and VMs can include RAM.
- R rolls back to the snapshot under the cursor. The confirm names the
  snapshot and its date. A running guest is started again; its status
  is read right before the rollback, and if it cannot be read the
  rollback does not run.
- D deletes the snapshot under the cursor, after a confirm.

`delete ct|vm <node> <vmid> -y` without the snapshot subcommand
destroys the whole guest. delete_snapshot therefore validates the name
first (letter first, then [A-Za-z0-9_-], not "current"), writes
"snapshot" into the argv as a literal, and checks the argv shape
before running it. A property test covers rejected names.

The info screen now scrolls, because four sections do not fit short
terminals. A description starting with "-" is refused, since it is a
positional argument and could be read as an option.

Live test on CT 104: take, roll back (started again) and delete. The
snapshot list, status, config and IPv4/IPv6 match the baseline.

Closes #8

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_cli.py

@@ -1003,3 +1003,248 @@ def test_not_backed_up_returns_vmids(fake):
 def test_not_backed_up_empty(fake):
     fake.result = ("[]", "", 0)
     assert cli.not_backed_up() == set()
+
+
+# --- snapshots (issue #8); spec: docs/plans/guest-tui-mvp.md ("Snapshots in the info screen") ---
+# Sections below name the spec bullet they cover.
+
+GOOD_NAMES = [
+    "a",
+    "snap1",
+    "tui_20251102_1430",
+    "A-b_c",
+    "x" * 40,
+    "snapshot",
+    "currentx",
+    "curren",
+]
+BAD_NAMES = [
+    "",
+    "current",
+    "Current",
+    "CURRENT",
+    "1snap",
+    "_snap",
+    "-snap",
+    "my snap",
+    "a,b",
+    ";rm",
+    "a;rm -rf",
+    "x" * 41,
+    "snäp",
+    "snap\n",
+    "snap ",
+]
+
+
+@pytest.mark.parametrize("name", GOOD_NAMES)
+def test_valid_snapname_accepts_pattern(
+    name,
+):  # valid_snapname: [A-Za-z][A-Za-z0-9_-]{0,39}
+    assert cli.valid_snapname(name) == name
+
+
+@pytest.mark.parametrize("name", BAD_NAMES)
+def test_valid_snapname_rejects(
+    name,
+):  # valid_snapname: ValueError outside pattern / "current"
+    with pytest.raises(ValueError):
+        cli.valid_snapname(name)
+
+
+@given(st.text())
+def test_delete_snapshot_with_rejected_name_raises_and_never_runs(name):
+    # delete_snapshot: name validated first; no subprocess call for an invalid name
+    try:
+        cli.valid_snapname(name)
+    except ValueError:
+        pass
+    else:
+        return  # accepted names are covered by the argv tests
+    with pytest.MonkeyPatch.context() as m:
+        run = FakeRun(m)
+        with pytest.raises(ValueError):
+            cli.delete_snapshot(CT, name)
+        with pytest.raises(ValueError):
+            cli.delete_snapshot(VM, name)
+        assert run.calls == []
+
+
+SNAPS_RAW = [
+    {"name": "old", "description": "first", "snaptime": 1_000, "parent": None},
+    {"name": "undated", "description": "", "snaptime": None, "parent": "old"},
+    {
+        "name": "current",
+        "description": "You are here!",
+        "snaptime": None,
+        "parent": "new",
+    },
+    {"name": "new", "description": "second", "snaptime": 3_000, "parent": "old"},
+    {"name": "mid", "description": "", "snaptime": 2_000, "parent": "old"},
+]
+
+
+def test_snapshots_drops_current_sorts_newest_first_null_last(fake):  # snapshots()
+    fake.result = (json.dumps(SNAPS_RAW), "", 0)
+    assert [s["name"] for s in cli.snapshots(CT)] == ["new", "mid", "old", "undated"]
+
+
+def test_snapshots_drops_current_case_insensitively(
+    fake,
+):  # snapshots(): current is not a snapshot
+    fake.result = (
+        json.dumps([{"name": "Current", "snaptime": None}, SNAPS_RAW[0]]),
+        "",
+        0,
+    )
+    assert [s["name"] for s in cli.snapshots(CT)] == ["old"]
+
+
+def test_snapshots_only_current_gives_empty_list(
+    fake,
+):  # snapshots(): "No snapshots" case
+    fake.result = (json.dumps([SNAPS_RAW[2]]), "", 0)
+    assert cli.snapshots(CT) == []
+
+
+@pytest.mark.parametrize(
+    "guest,kind",
+    [(CT, "lxc"), (VM, "qemu")],
+)
+def test_snapshots_argv_uses_qemu_or_lxc(
+    fake, guest, kind
+):  # CLI facts: get guest snapshots
+    fake.result = ("[]", "", 0)
+    cli.snapshots(guest)
+    assert fake.argv == [
+        "cv4pve-cli", "get", "guest", "snapshots", "mainframe", kind, str(guest["vmid"]), "-o", "json",
+    ]  # fmt: skip
+
+
+def test_snapshots_failure_raises_clierror(
+    monkeypatch,
+):  # snapshots(): failure surfaces as CliError
+    FakeRun(monkeypatch, "Error: boom", returncode=1)
+    with pytest.raises(cli.CliError):
+        cli.snapshots(CT)
+
+
+def test_take_snapshot_ct_argv_has_no_vmstate_and_wait_last(fake):  # take_snapshot
+    cli.take_snapshot(CT, "snap1", "hello")
+    assert fake.argv == [
+        "cv4pve-cli", "create", "ct", "snapshot", "mainframe", "100", "snap1", "hello", "--wait",
+    ]  # fmt: skip
+
+
+def test_take_snapshot_vm_without_vmstate(fake):  # take_snapshot
+    cli.take_snapshot(VM, "snap1", "hello")
+    assert fake.argv == [
+        "cv4pve-cli", "create", "vm", "snapshot", "mainframe", "108", "snap1", "hello", "--wait",
+    ]  # fmt: skip
+
+
+def test_take_snapshot_vm_with_vmstate_before_wait(
+    fake,
+):  # take_snapshot: --vmstate 1 (VM only)
+    cli.take_snapshot(VM, "snap1", "hello", vmstate=True)
+    assert fake.argv == [
+        "cv4pve-cli", "create", "vm", "snapshot", "mainframe", "108", "snap1", "hello",
+        "--vmstate", "1", "--wait",
+    ]  # fmt: skip
+
+
+def test_take_snapshot_ct_ignores_vmstate(fake):  # take_snapshot: vmstate only for a VM
+    cli.take_snapshot(CT, "snap1", "hello", vmstate=True)
+    assert "--vmstate" not in fake.argv and fake.argv[-1] == "--wait"
+
+
+def test_take_snapshot_default_description(
+    fake,
+):  # take_snapshot: description or "cv4pve-tui"
+    cli.take_snapshot(CT, "snap1")
+    assert fake.argv[7] == "cv4pve-tui"
+
+
+def test_take_snapshot_empty_description_falls_back(
+    fake,
+):  # take_snapshot: `description or "cv4pve-tui"`
+    cli.take_snapshot(VM, "snap1", "")
+    assert fake.argv[7] == "cv4pve-tui"
+
+
+@pytest.mark.parametrize("name", ["", "current", "1x", "a b", ";rm"])
+def test_take_snapshot_invalid_name_no_call(
+    fake, name
+):  # take_snapshot: name validated first
+    with pytest.raises(ValueError):
+        cli.take_snapshot(VM, name, "d")
+    assert fake.calls == []
+
+
+@pytest.mark.parametrize("guest,kind", [(CT, "ct"), (VM, "vm")])
+def test_rollback_argv_without_start(fake, guest, kind):  # rollback_snapshot
+    cli.rollback_snapshot(guest, "snap1")
+    assert fake.argv == [
+        "cv4pve-cli", "do", "rollback", kind, "mainframe", str(guest["vmid"]), "snap1", "-y", "--wait",
+    ]  # fmt: skip
+
+
+@pytest.mark.parametrize("guest,kind", [(CT, "ct"), (VM, "vm")])
+def test_rollback_argv_with_start(
+    fake, guest, kind
+):  # rollback_snapshot: [--start 1] -y --wait
+    cli.rollback_snapshot(guest, "snap1", start=True)
+    assert fake.argv == [
+        "cv4pve-cli", "do", "rollback", kind, "mainframe", str(guest["vmid"]), "snap1",
+        "--start", "1", "-y", "--wait",
+    ]  # fmt: skip
+
+
+@pytest.mark.parametrize("name", ["", "current", "Current", "9", "a b", "a,b"])
+def test_rollback_invalid_name_no_call(fake, name):  # rollback_snapshot: name validated
+    with pytest.raises(ValueError):
+        cli.rollback_snapshot(CT, name, start=True)
+    assert fake.calls == []
+
+
+@pytest.mark.parametrize("guest,kind", [(CT, "ct"), (VM, "vm")])
+def test_delete_snapshot_exact_argv(fake, guest, kind):  # delete_snapshot
+    cli.delete_snapshot(guest, "snap1")
+    assert fake.argv == [
+        "cv4pve-cli", "delete", kind, "snapshot", "mainframe", str(guest["vmid"]), "snap1", "-y", "--wait",
+    ]  # fmt: skip
+
+
+@given(
+    name=st.from_regex(r"[A-Za-z][A-Za-z0-9_-]{0,39}", fullmatch=True).filter(
+        lambda n: n.lower() != "current"
+    ),
+    guest=st.sampled_from([CT, VM]),
+)
+def test_delete_never_produces_guest_destroying_form(name, guest):
+    # DANGER: `delete <kind> <node> <vmid> -y` destroys the guest; "snapshot" must sit at index 3
+    kind = {"lxc": "ct", "qemu": "vm"}[guest["type"]]
+    with pytest.MonkeyPatch.context() as m:
+        run = FakeRun(m)
+        cli.delete_snapshot(guest, name)
+        argv = run.argv
+    assert argv[1:3] == ["delete", kind]
+    assert argv[3] == "snapshot"  # never the node directly after the kind
+    assert (
+        argv[4] == guest["node"] and argv[5] == str(guest["vmid"]) and argv[6] == name
+    )
+    assert argv[1:3] != ["delete", kind] or argv[3] != guest["node"]
+
+
+def test_delete_with_snapshot_like_name_still_has_snapshot_at_index_3(fake):
+    # a valid name equal to the subcommand word must not shift the positions
+    cli.delete_snapshot(CT, "snapshot")
+    assert fake.argv[3:7] == ["snapshot", "mainframe", "100", "snapshot"]
+
+
+def test_take_snapshot_refuses_description_that_looks_like_an_option(fake):
+    with pytest.raises(ValueError):
+        cli.take_snapshot(
+            {"vmid": 104, "node": "mainframe", "type": "lxc"}, "snap1", "-y"
+        )
+    assert fake.calls == []