openai/gpt-chat-latest → A (3:1)

Side A fixes a concrete concurrency bug by shortening the lifetime of `state.reduced.read().await` guards before later `read()`/`write()` operations, explicitly preventing Tokio `RwLock` self-deadlocks in `RoomCreate` and `RoomGrant`, and adds an integration test covering private room creation. Side B is largely a type-safety refactor that replaces many `String` usages with `CanonicalItemUrl` and adds `Deref` implementations, improving API cleanliness but with less direct impact on runtime correctness than the deadlock fix.