openai/gpt-chat-latest → A (3:2)

Side A introduces a lasting URL routing redesign by centralizing private-room path encoding/decoding (`room_route_segment`/`room_id_from_route_segment`), replacing ad hoc `split_once('/')` logic across routing, link generation, navigation, tests, and constants such as `ROOM_SHORT_ID_LEN`. It also improves canonical URL handling with reusable normalization utilities (including YouTube normalization and stable external URL canonicalization), whereas Side B primarily adds an offline developer tool (`sorterc`) that reuses existing validation and ranking logic without changing the application's core behavior.