openai/gpt-chat-latest → B (9:1)

Side B performs a broad architectural refactor by introducing a structured `ItemId` type, replacing `CanonicalItemUrl` across reducer state, ranking, RPC, routing, HTML, tests, and type exports, enabling stronger typing and reducing string-based identity handling. Side A mainly removes a duplicate `forum.rs` and formalizes `forum/mod.rs` as the sole module root—a useful cleanup that fixes module resolution ambiguity, but it largely reorganizes existing code rather than changing core project capabilities.