fix(api-server): guard json.loads against corrupted SQLite data in response cache

The ResponseStore.get() method calls json.loads(row[0]) without any
error handling. If the SQLite responses table contains corrupted JSON
data (e.g. from a crash mid-write or disk corruption), this raises
an unhandled JSONDecodeError that propagates to the caller.

Fix: wrap in try/except (json.JSONDecodeError, TypeError). On parse
failure, log a warning, evict the corrupted entry from the cache, and
return None (consistent with the function's Optional return type).

gateway/platforms/api_server.py

@@ -423,7 +423,19 @@ class ResponseStore:
             (time.time(), response_id),
         )
         self._conn.commit()
-        return json.loads(row[0])
+        try:
+            return json.loads(row[0])
+        except (json.JSONDecodeError, TypeError):
+            logger.warning(
+                "Corrupted JSON in response store for id=%s, evicting entry",
+                response_id,
+            )
+            self._conn.execute(
+                "DELETE FROM responses WHERE response_id = ?",
+                (response_id,),
+            )
+            self._conn.commit()
+            return None
 
     def put(self, response_id: str, data: Dict[str, Any]) -> None:
         """Store a response, evicting the oldest if at capacity."""