refactor: modularity fixes + plugin registry + compiled research

purpose_agent/streaming.py

@@ -228,7 +228,7 @@ class AsyncOrchestrator:
             current_state = new_state
 
         # Post-task (run in background)
-        await asyncio.to_thread(self.orch._post_task, trajectory, [])
+        await asyncio.to_thread(self.orch.post_task, trajectory, [])
 
         yield StreamEvent("task_end", {
             "total_steps": len(trajectory.steps),