/flywheel-cleanup

First action: Run git worktree list --porcelain via Bash and diff the result against .pi-flywheel/checkpoint.json to identify orphaned worktrees before prompting the user.

Clean up orphaned git worktrees.

1. Run git worktree list --porcelain via Bash to list all active worktrees.
2. Compare against tracked worktrees in .pi-flywheel/checkpoint.json (if any).
3. Identify orphaned worktrees: exist on disk but not tracked in checkpoint, or checkpoint is gone.
4. For each orphan:
   • Check for uncommitted changes: git -C <path> status --short
   • If dirty, warn the user and ask whether to auto-commit before removing.
   • If the user wants to auto-commit: run git -C <path> add -A && git -C <path> commit -m "wip: orphaned worktree cleanup"
5. List what will be removed and ask for confirmation.
6. For each confirmed orphan: git worktree remove --force <path> via Bash.
7. Report: "Cleaned N worktrees (M with auto-committed changes)."