fix(gateway): atomic writes for sibling recovery/dedup state files

Widen PR #17842's atomic-write fix to two sibling sites that exhibit the
same 'partial JSON on interrupted write' class of bug:

- gateway/platforms/feishu.py: dedup state (_dedup_state_path)
- gateway/platforms/helpers.py: ParticipatedThreadTracker save

Both are small recovery/coordination files that get rewritten frequently and
break cross-restart dedup if left partial.

gateway/platforms/feishu.py

@@ -141,6 +141,7 @@ from gateway.platforms.base import (
 )
 from gateway.status import acquire_scoped_lock, release_scoped_lock
 from hermes_constants import get_hermes_home
+from utils import atomic_json_write
 
 logger = logging.getLogger(__name__)
 
@@ -3804,7 +3805,7 @@ class FeishuAdapter(BasePlatformAdapter):
             recent = self._seen_message_order[-self._dedup_cache_size:]
             # Save as {msg_id: timestamp} so TTL filtering works across restarts.
             payload = {"message_ids": {k: self._seen_message_ids[k] for k in recent if k in self._seen_message_ids}}
-            self._dedup_state_path.write_text(json.dumps(payload, ensure_ascii=False), encoding="utf-8")
+            atomic_json_write(self._dedup_state_path, payload, indent=None)
         except OSError:
             logger.warning("[Feishu] Failed to persist dedup state to %s", self._dedup_state_path, exc_info=True)