openai/gpt-chat-latest → A (4:1)

Side A introduces a durable routing abstraction (`room_route_segment`/`room_id_from_route_segment` and `ROOM_SHORT_ID_LEN`), updates all server routes and URL generation to use a single encoded room path format, and adds URL normalization utilities (including canonicalization of external URLs such as YouTube links) with accompanying tests. Side B fixes a real Reddit import bug by attaching imported children directly under the fetched parent and improves unranked child labels using stored titles, but its impact is narrower and localized compared with Side A's project-wide API and URL consistency improvements.