Room server: message search and pagination

[YeshuaGod22]

Background

The room server currently stores all messages in memory and serves them as a flat array. There's no search API and no pagination — clients get the entire chatlog.

What's needed

• GET /api/room/:name/chatlog?limit=50&before=<msgId> — paginated access
• GET /api/room/:name/search?q=<query> — full-text search across room messages
• Consider indexing strategy for rooms with 5000+ messages

Constraints

• Room server must remain stateless with respect to LLMs (rule 3)
• Current persistence is a single rooms.json file — this may need to evolve
• The room server contract is in contracts/ROOM-SERVER.md

Labels: good-first-issue, infrastructure