chore(lint): make the repository ruff-clean under the strict select

Clear the deferred full-repo lint backlog so the whole tree passes the strict
ruff select (E,W,F,I,B,UP,C4,SIM). Mechanical fixes dominate: import sorting,
pep585/604 annotations, dropped dead imports, and whitespace. The few semantic
changes are behavior-preserving: declare __all__ on the agent_utils and
alpha_vantage re-export hubs; expand 'from x import *' to explicit names; use
immutable tuple defaults instead of mutable list defaults; contextlib.suppress
for try/except/pass; and narrow an over-broad assertRaises.

cli/stats_handler.py

@@ -1,9 +1,9 @@
 import threading
-from typing import Any, Dict, List, Union
+from typing import Any
 
 from langchain_core.callbacks import BaseCallbackHandler
-from langchain_core.outputs import LLMResult
 from langchain_core.messages import AIMessage
+from langchain_core.outputs import LLMResult
 
 
 class StatsCallbackHandler(BaseCallbackHandler):
@@ -19,8 +19,8 @@ class StatsCallbackHandler(BaseCallbackHandler):
 
     def on_llm_start(
         self,
-        serialized: Dict[str, Any],
-        prompts: List[str],
+        serialized: dict[str, Any],
+        prompts: list[str],
         **kwargs: Any,
     ) -> None:
         """Increment LLM call counter when an LLM starts."""
@@ -29,8 +29,8 @@ class StatsCallbackHandler(BaseCallbackHandler):
 
     def on_chat_model_start(
         self,
-        serialized: Dict[str, Any],
-        messages: List[List[Any]],
+        serialized: dict[str, Any],
+        messages: list[list[Any]],
         **kwargs: Any,
     ) -> None:
         """Increment LLM call counter when a chat model starts."""
@@ -57,7 +57,7 @@ class StatsCallbackHandler(BaseCallbackHandler):
 
     def on_tool_start(
         self,
-        serialized: Dict[str, Any],
+        serialized: dict[str, Any],
         input_str: str,
         **kwargs: Any,
     ) -> None:
@@ -65,7 +65,7 @@ class StatsCallbackHandler(BaseCallbackHandler):
         with self._lock:
             self.tool_calls += 1
 
-    def get_stats(self) -> Dict[str, Any]:
+    def get_stats(self) -> dict[str, Any]:
         """Return current statistics."""
         with self._lock:
             return {