ramwin/dsh-branch-cleaner

Redundant branch cleaner: finds branches whose work already landed in the mainline — merged, squash-merged, patch-equivalent after rebase or cherry-pick, upstream-gone, or PR-merged — and deletes them when asked. It only reports by default, never switches branches or rebases, and backs every deleted local branch up under refs/backup/branch-cleaner/ (deleting remote branches has no backup).