- module-level Map<string, {count, timer}> keyed by ${listId}:${actorId}
- sliding window: each call within window resets timer and increments count
- fires dispatch(listId, actorId, count) once on timer expiry; map entry self-deletes
- actorId passed as second arg so caller can apply excludeUserId=actorId (D-03)
- default windowMs=45000; injected dispatch keeps module pure and testable