openai/gpt-chat-latest → A (3:2)

Side A strengthens the project's type safety by changing `resolve_item` to return `CanonicalItemUrl`, propagating canonical URL types through ranking, validation, connectivity, and pair-selection code, and adding `Deref<Target=str>` for URL newtypes to reduce string conversions. Side B removes legacy GitDiscovery projection paths and requires Evidence-only data for epoch/commit pages, simplifying the codebase but intentionally dropping backward compatibility and mainly affecting presentation and historical data handling.