feat(gateway): add AsyncSessionDB offload facade

hermes_state.py

@@ -14,6 +14,7 @@ Key design decisions:
 - Session source tagging ('cli', 'telegram', 'discord', etc.) for filtering
 """
 
+import asyncio
 import json
 import logging
 import random
@@ -5525,3 +5526,20 @@ class SessionDB:
                 (error[:500], session_id),
             )
         self._execute_write(_do)
+
+
+class AsyncSessionDB:
+    """Async door onto SessionDB: offloads each call via asyncio.to_thread so a blocking SQLite call never freezes the event loop. Generic forwarder — the audit confirms no method returns a live cursor/generator."""
+
+    def __init__(self, db: "SessionDB") -> None:
+        self._db = db
+
+    def __getattr__(self, name: str):
+        attr = getattr(self._db, name)
+        if not callable(attr):
+            return attr
+
+        async def _offloaded(*args, **kwargs):
+            return await asyncio.to_thread(attr, *args, **kwargs)
+
+        return _offloaded