openai/gpt-chat-latest → A (6:1)

Side A performs a substantial architectural migration from the string-based `CanonicalItemUrl` to a structured `ItemId` across reducer state, ranking, routing, APIs, and tests, while introducing new `item_id` and `item_wire` modules and updating link generation to use typed identities. Side B fixes important OAuth test infrastructure issues (query parsing, request body reading, redirect handling, null checks, and mock robustness), but those changes are confined to test mocks and E2E reliability rather than the project's core design.