Squash-merged branches never show in git branch --merged

In repos that squash-merge PRs, git branch --merged origin/main lists nothing, even for fully merged branches, because the squash commit has a different SHA. To check that a stale branch is safe to delete, compare its tip SHA to the merged PR's head: gh pr view N --json headRefOid. If they match, nothing was pushed after the merge. Also run git fetch --prune: local branches whose upstream is shown as gone are usually merged PR branches that GitHub auto-deleted.