Raphael v2.2

Research Agent: ResearchAgent implemented in ai.rs — handles complex multi-step queries by decomposing, gathering, and synthesizing information in a background thread.
POST /api/agent/research: Triggers a research job asynchronously. Returns a job ID immediately so Discord interactions don't time out waiting for results.
GET /api/agent/status/:id: Poll endpoint for checking job progress and retrieving results once complete.
Non-Blocking Architecture: Agents run fully detached from the request lifecycle — long-running research tasks no longer risk hitting Discord's response timeout.