openai/gpt-chat-latest → A (4:1)

Side A makes a behavioral change by removing a dead zero-ratio early return in `GroupState::apply_vote`, relying on existing parser/browser validation and `add_edge_weight` to skip zero-weight edges. It also updates tests to verify that items and pairs are still registered while no edges are created, reflecting the intended reducer semantics. Side B is primarily a large refactoring that deletes the monolithic `forum.rs` and redistributes code into submodules without introducing significant new functionality.