[Feature Request] Add merge verification option to ExitWorktree for safe worktree cleanup without data loss

Question

**Bug Description**
ExitWorktree has two options: keep the tree around forever, or discard it and get data loss warnings. I / my Claudes need a third option: verify that this worktree's commits have been merged back into main, and then close the worktree having checked that data is *not* being lost. I'm doing local solo development, and features do not go through github or equiv. I want to be able to call an agent's feature complete and drop the worktree and context, but the current tooling does