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.

tradingagents/llm_clients/base_client.py

@@ -1,6 +1,6 @@
-from abc import ABC, abstractmethod
-from typing import Any, Optional
 import warnings
+from abc import ABC, abstractmethod
+from typing import Any
 
 
 def normalize_content(response):
@@ -25,7 +25,7 @@ def normalize_content(response):
 class BaseLLMClient(ABC):
     """Abstract base class for LLM clients."""
 
-    def __init__(self, model: str, base_url: Optional[str] = None, **kwargs):
+    def __init__(self, model: str, base_url: str | None = None, **kwargs):
         self.model = model
         self.base_url = base_url
         self.kwargs = kwargs