openai/gpt-chat-latest → B (4:1)

Side B substantially redesigns the pair-selection algorithm by replacing per-candidate priority/key computation with a staged approach: linear graph-growth scans (`suggest_grow_pair`), a single rank-centrality pass with adjacent-rank zipping (`zip_adjacent_pair`), and simplified fallback logic. This removes the previous O(n²)-style ranking work while preserving behavior through targeted helper functions, whereas Side A is a focused concurrency improvement that simply precomputes `room_members_section_markup` and drops an `RwLock` read guard before expensive HTML rendering to reduce lock contention.