RSC → React Query handoff

Server prefetches the list with a 200ms artificial delay, ships the query cache in the HTML. The client useQuery reads from the pre-hydrated cache — zero loading flash. Stars are optimistic mutations with rollback on error.

Open DevTools → Network. The initial page load contains the serialized query cache. Subsequent mutations make a new server-fn RPC, but the cache is updated optimistically before the round-trip completes.