gh-clean-brancheslisted

# Clean Branches Prune stale local branches. Two kinds of branch debt cleaned up in one pass: branches whose remote is gone, and feature branches already merged into main. Triggered by: `/gh-clean-branches`, "clean branches", "prune branches", "delete stale branches". ## Steps ### 1. Sync remote refs ```bash git fetch --prune ``` This removes remote-tracking refs for branches that no longer exist on the remote. Required before detection — without it, gone branches won't show as gone. ### 2. Detect branches with gone remotes ```bash git branch -vv | grep ': gone]' ``` Lists local branches whose upstream tracking remote has been deleted (e.g., merged PRs where the branch was auto-deleted on GitHub). ### 3. Detect merged feature branches ```bash git branch --merged main ``` Also try `master` if `main` doesn't exist. Lists local branches fully merged into main. Exclude: `main`, `master`, `develop`, `staging`, and the currently checked-out branch. ### 4. Present combined candidate list Show a single deduplicated table: ``` Branches to delete: ┌──────────────────────────────┬─────────────────────────────┐ │ Branch │ Reason │ ├──────────────────────────────┼─────────────────────────────┤ │ feat/old-login │ remote gone │ │ fix/button-color │ merged into main │ │ chore/deps-update │ remote gone + merged │ └──────────────────────────────┴────