openai/gpt-chat-latest → A (5:1)

Side A implements a substantial, cross-cutting feature set: persistent theme selection via validated cookies and a new `/theme` endpoint, propagates theme state through page rendering and authentication so login preserves the user's theme, and adds room-aware URL generation for RPC/API responses with dedicated helper functions and tests. Side B makes useful but narrower fixes—passing browser delegate metadata out-of-band, preventing an incorrect fallback when too few sibling items exist, removing a redundant swap button, and renaming `/vote/compare` to `/vote`—but its impact is much more localized.