openai/gpt-chat-latest → B (4:1)

Side B performs a real codebase refactor by extracting forum functionality into focused modules (`access.rs`, `ingest.rs`, `nav.rs`, `new_thread.rs`, `room_members.rs`), introducing reusable components like `ThreadNav`, and moving existing UI logic without changing behavior, which improves maintainability. Side A mostly adds a detailed migration plan (`plan.md`) plus a thin `RouteContext` wrapper around `ThreadNav`; while useful as guidance, it leaves the underlying architecture largely unchanged.