Intelligence Greeting

Fired when an intelligence-query run lands at CP1 with a grounded synthesis. research_query is fire-and-forget, so the persona delivers the actual answer here — narrated from the engine-grounded narratives. Idempotent per session; returns null when the parked run isn't an intelligence query (e.g. a normal start_run also reaches CP1), so the frontend can call it on every CP1 edge.