Removing
dd on a worktree in Repos removes it; v to select several, then d. A confirmation lists what will go, and what
will be kept and why.

Removing a worktree also removes its local branch (delete_branch under [cleanup], on by default); the branch on
GitHub is left alone. Sessions working there move to History.
- A worktree with uncommitted changes.
- A worktree with unpushed commits, or a branch that was never pushed.
- A worktree whose status is unknown.
- A worktree used by a pinned session.
The same rules hold for deleting a session and for cleanup.