openai/gpt-chat-latest → A (4:1)

Side A makes a substantial architectural cleanup by removing legacy GitDiscovery projection paths, requiring evidence metadata on Emission records, simplifying epoch/commit pages to operate only on Evidence envelopes, and updating tests to match the new invariant. Side B fixes a real bug by defining GITHUB_API_BASE_URL to avoid a NameError, but it is a small localized configuration fix compared with A's broader, lasting simplification of the evidence model.