openai/gpt-chat-latest → A (9:1)

Side A delivers substantial new functionality: browser session cookies, login/logout flow, web posting, room-aware thread views, private room access checks, new routes, and reusable helpers such as `rpc_post_with_bearer`, fundamentally restoring and expanding the web UI. Side B is primarily a refactor that consolidates `/post`-style handlers into a single `/ui` dispatch (`resolve_web_session`, moving logic from `web_post.rs` into `ui_html.rs`) and updates forms/tests to use `__rpc__`, improving organization but adding comparatively little new behavior.