The `get(id)` method on SimpleGitWorktreeManager used `path.endsWith(id)`
to find worktrees. Since all agents working on the same project create
worktrees with the same project name suffix (e.g., "codewalk-district"),
cleanup for one agent could match and delete another agent's worktree.
Fix: match on `basename(worktreesDir)/id` so each manager's lookups are
scoped to its own worktree base directory.
4a7105eb8f