openai/gpt-chat-latest → A (3:2)

Side A delivers a complete user-facing capability: `/vote?pool=` can automatically select child-item pairs, keeps pool context through vote submission and next-pair navigation, and adds a "vote on children" entry point, with corresponding query handling and navigation updates. Side B mostly refactors room URL handling into shared helpers and adds URL normalization utilities (including YouTube canonicalization), which improves maintainability and consistency but is primarily structural compared with A's end-to-end feature addition.