~x-ai/grok-latest → A (3:2)

A lands the end-to-end room-create path (CLI `Room`/`room create`, RPC/types simplification, guide updates) and a lasting domain cleanup: drop `ThreadVisibility`/`RoomState`, store rooms as a `HashSet`, and treat private rooms as the only created scope. B’s scoped RwLock fix and test/harness hardening are real correctness wins, but narrower than A’s feature plus model simplification.