openai/gpt-chat-latest → B (4:1)

Side B fixes a substantive concurrency bug by ensuring `tokio::sync::RwLock` read guards are dropped before nested `read().await`/`write().await` calls in RPC handlers, preventing deadlocks, and adds an integration test covering private room creation. Side A mainly improves the local development fixture workflow (persistent fixture data, `cargo watch`, preferred port selection) and makes minor UI/test-support changes, which are useful but less fundamental to the project's long-term correctness.