openai/gpt-chat-latest → A (4:1)

Side A performs a project-wide architectural migration from `CanonicalItemUrl` string keys to a structured `ItemId`, adding the new `item_id`/`item_wire` modules and propagating the type through reducers, ranking, routing, APIs, HTML, and tests while preserving normalization and serialization behavior. Side B adds a useful vote comparison UI, pair-selection logic, and related tests, but its scope is primarily a feature layer, whereas Side A changes the project's core identity model in a way that is likely to support many future features and reduce string-based errors.