openai/gpt-chat-latest → A (4:1)

Side A makes a foundational change to the project's identity model by introducing a composable URL canonicalization subsystem (`server/src/url_rules/`), switching `ItemId` to canonical full URLs, centralizing parent/breadcrumb logic, and updating projection/event parsing so stored IDs are normalized consistently. Side B delivers a real bug fix for the external garden index and improves GitHub resolver rendering with rich cards, but most of its changes are feature/UI-oriented and a module reorganization rather than a core architectural improvement.