Plan slug persists in input-box corner after ExitPlanMode (and after deleting the plan file)

What happens

After creating a plan in plan mode and approving ExitPlanMode, the auto-generated plan slug (e.g. avatar-enumerable-id-security) stays pinned in the top-right corner of the input box for the rest of the session — implying you're still in a plan context that ended long ago. It persists even after the plan file is deleted from ~/.claude/plans/.

Repro

1. Enter plan mode; create a plan (a slug is generated).
2. Approve ExitPlanMode; keep working — file edits and git commits succeed, confirming plan mode is genuinely over.
3. Delete the plan file from ~/.claude/plans/.
4. The slug still shows in the input-box corner.

Expected: the label clears when plan mode ends (or at the latest when the plan file is removed), since the session is no longer in that context.

Actual: it remains for the rest of the session until /clear.

Workaround: /clear resets session state and removes it.

Environment: Claude Code 2.1.226 (TUI), Linux.