~anthropic/claude-sonnet-latest → A (6:4)

Side A removes dead demo-counter scaffolding and, more importantly, introduces a real architectural improvement: an async settlement worker (settlement.rs) that batches vote writes and caches ranking scores, decoupling expensive Bradley-Terry recomputation from the request path and switching ranking_panel to a read lock. Side B is a much smaller, purely cosmetic fix (rank row color gradient using score-based min-max normalization instead of list position) that improves UI polish but has far less lasting architectural or correctness impact.