openai/gpt-5.2-chat → B (9:1)

Commit B introduces a substantial theming system refactor and extension: adds theme cookie handling, normalization, POST /theme endpoint, layout changes, propagation of theme through many HTML handlers, updates to auth flows to preserve theme, new helper functions for room-aware URL generation, and extensive RPC adjustments plus tests. It spans multiple modules and meaningfully changes behavior. Commit A is purely formatting/reordering without functional changes. Therefore B contributes far more.