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_capabilities.py

@@ -1,9 +1,10 @@
 """Unit tests for the LLM capability table."""
 
+from dataclasses import FrozenInstanceError
+
 import pytest
 
 from tradingagents.llm_clients.capabilities import (
-    ModelCapabilities,
     get_capabilities,
 )
 
@@ -119,5 +120,5 @@ class TestDefault:
 def test_capabilities_dataclass_is_frozen():
     """Capability rows are immutable so they can be safely shared."""
     caps = get_capabilities("deepseek-chat")
-    with pytest.raises(Exception):
+    with pytest.raises(FrozenInstanceError):
         caps.supports_tool_choice = False  # type: ignore[misc]