Removing a worktree no longer deletes folders that hold git's own files

A worktree is an extra working copy of a git repository in its own folder. When Claude Code drops a worktree's registration and the folder holds files that belong in a git directory (objects, config, packed-refs, hooks or worktrees), it now leaves the folder in place and shows a warning. Git deletes it on its next prune or git gc.

Before, Claude Code removed the whole folder, and if that failed, removed only the files git writes there.