fix: add traceback logging to _store_session for debugging

- Restore datetime objects instead of isoformat strings for db driver handling
- Print full traceback when session storage fails to identify exact error source

harnessed_reasoning/core.py

@@ -625,14 +625,16 @@ class HermesReasoningEngine:
                 'safety_violations_json': json.dumps(violations, ensure_ascii=False),
                 'final_decision_json': json.dumps({'status': status}),
                 'status': status,
-                'created_at': datetime.now().isoformat(),
-                'updated_at': datetime.now().isoformat(),
+                'created_at': datetime.now(),
+                'updated_at': datetime.now(),
             }
             async with self.db.sqlorContext('default') as sor:
                 res = await sor.C('harnessed_reasoning_sessions', data)
                 info(f"Session stored: {session_id}, result={res}")
         except Exception as e:
+            import traceback
             error(f"Failed to store session details: {e}")
+            error(f"Traceback:\n{traceback.format_exc()}")
 
     async def _update_session_status(self, session_id: str, status: str):
         """Update session status."""