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.

tests/test_api_key_env.py

@@ -3,14 +3,12 @@
 from __future__ import annotations
 
 import os
-from pathlib import Path
 from unittest.mock import patch
 
 import pytest
 
 from tradingagents.llm_clients.api_key_env import PROVIDER_API_KEY_ENV, get_api_key_env
 
-
 # ---- Mapping coverage -----------------------------------------------------
 
 
@@ -71,6 +69,7 @@ def test_case_insensitive_lookup():
 def cli_utils(monkeypatch):
     """Import cli.utils with a fresh environment so module-level state is consistent."""
     import importlib
+
     import cli.utils as cli_utils_module
     return importlib.reload(cli_utils_module)