No user-side exit from plan mode when triggered accidentally

Problem

Once /plan is active, there is no way for the user to exit plan mode themselves. The only exit path is for Claude to call ExitPlanMode and the user to approve the resulting dialog — but this dialog is easy to accidentally dismiss (Escape, clicking X), which puts the user back in plan mode with no escape.

Steps to Reproduce

1. Accidentally run /plan during a casual Q&A conversation (not a coding task)
2. Try to exit plan mode by running /plan again — it says "Already in plan mode. No plan written yet."
3. Try Escape — does not exit
4. Try /exit-plan — command does not exist
5. Check /help — no plan mode exit option listed
6. Only way out: ask Claude to call ExitPlanMode and approve the dialog

Expected Behaviour

/plan should be a clean toggle — running it again should exit plan mode immediately, regardless of whether a plan has been written. Or there should be a dedicated /exit-plan or /cancel-plan command the user can run at any time.

Why This Matters

Plan mode is useful for coding tasks, but it gets triggered easily during normal conversation. When there is no actual plan to approve, the ExitPlanMode approval dialog is confusing ("approve what?") and dismissing it accidentally traps the user in plan mode indefinitely.

Environment

• Claude Code CLI
• macOS