Reset the terminal before opening the LXC shell

Write ESC c, the sequence `reset` sends, inside suspend() right before
ssh. The container shell then starts on a clean screen with no
leftover TUI terminal modes. It runs locally, so the container does
not need `reset` installed and `pct enter` is unchanged.

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

docs/plans/guest-tui-mvp.md

@@ -210,6 +210,10 @@ root's `authorized_keys` (verified: `ssh -o BatchMode=yes root@mainframe pct sta
 - 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.