openai/gpt-chat-latest → A (4:1)

Side A fixes a concrete user-visible bug by changing rank gradient calculations from global ranking offsets to per-group indices, adds regression tests for the highlighting behavior, and aligns vote-history slider polarity with supporting helper functions and tests. Side B is primarily a structural refactor that removes a duplicate `forum.rs` and reorganizes code into `forum/` modules without introducing significant new behavior, improving maintainability but providing less direct lasting functionality.