~x-ai/grok-latest → B (2:5)

B adds a real CLI `room create` path and simplifies the core domain by dropping ThreadVisibility/RoomState in favor of a private-room HashSet, with matching RPC, reducer, docs, and tests—lasting product and model value. A only repairs test doubles (request body vs input stream, query split regex, nil token/state, handler try/catch) and Playwright helpers so E2E auth runs again, which is necessary but test-only.