Finalize

Finalize a merged issue — close the GitHub issue, remove its lifecycle/coordination labels, close and clean any issue recorded to close with it, and remove the issue's git worktree. Final stage of the flow delivery workflow (see docs/workflow.md). Runs once the FEATURE PR has merged — by the owner's squash-merge by default, or by `implement` itself if the `merge-on-green` label was set or this run's the issue's owner instructions said to auto-merge. Does NOT touch the OpenSpec archive — that's `project-manager`'s job, done in bulk across several issues at once via `/spec-flow:archive`, once enough have piled up. This skill never merges the feature PR and never opens a PR …