branch-cleanup

Find and clean up merged branches, stale worktrees, and fully-merged Graphite stacks. Use whenever the user wants to tidy up branches or worktrees — "clean up my branches", "delete merged branches", "I've got too many branches", "prune worktrees", "what's safe to delete", "did this ever get merged", or after PRs land and they ask what's left to clear out. Handles squash-merges (which git branch --merged silently misses), Graphite stacks, and worktrees left behind by Claude Code and Codex/Cursor sessions. Always reports before deleting, separates what is provably merged from what needs a decision, and never touches remote branches.