feat: auto-trigger reviewer after owner completion with round trip limit

- Owner finishes → auto mark review_ready → reviewer executes
- Reviewer finishes → task back to active → owner can respond
- Automatic ping-pong until consensus or round trip limit
- PAIRED_MAX_ROUND_TRIPS env var (default 10, 0 = unlimited)
- round_trip_count tracked per task in DB

src/types.ts

@@ -62,6 +62,7 @@ export interface PairedTask {
   source_ref: string | null;
   plan_notes: string | null;
   review_requested_at: string | null;
+  round_trip_count: number;
   status: PairedTaskStatus;
   created_at: string;
   updated_at: string;