openai/gpt-chat-latest → A (5:2)

Side A delivers substantial end-user functionality by wiring the web UI back together: it adds browser login/logout with session cookies, authenticated web posting, room-aware thread pages, routing, and reusable helpers for principal resolution, enabling the application to be used through the browser. Side B is a solid internal refactor that strengthens type safety by propagating `CanonicalItemUrl` and adding `Deref` implementations, but it mostly restructures existing code without adding comparable user-visible capability.