Sync the current feature/PR branch with trunk — fetch latest master/main, rebase by default or merge it in, resolve conflicts, verify, and optionally push. Use when asked to "pull down latest master, resolve conflicts, commit and push", update a stale branch, rebase onto trunk, or refresh a PR against main/master before merge. Arguments are positional: push|keep-local then rebase|merge, defaulting to push rebase.
