fix retry in query handler

src/wandbot/rag/query_handler.py

@@ -294,7 +294,7 @@ def _load_chain(self, model: ChatOpenAI) -> Runnable:
 
         # Add retry specifically for validation errors
         query_enhancer_chain = base_query_enhancer.with_retry(
-            retry_if_exception_type=ValidationError,
+            retry_if_exception_type=(ValidationError,),
             wait_exponential_jitter=True,  # Add jitter to prevent thundering herd
             stop_after_attempt=6,
         )