Companion

Install the start observer + the finalization-push observer. Call once from Application.onCreate. Watches (operations, syncStatus, locked) and starts the FGS whenever an operation or sync is in flight; the service self-stops on completion / lock. A SEPARATE observer rides the operation terminal stream and posts the dismissible finalization notification (#264) — app-scoped, so it fires even after the FGS has already stopped. No-op if not called.