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_no_data_handling.py

@@ -14,7 +14,7 @@ from unittest import mock
 import pandas as pd
 import pytest
 
-from tradingagents.dataflows import stockstats_utils, interface
+from tradingagents.dataflows import interface, stockstats_utils
 from tradingagents.dataflows.config import set_config
 from tradingagents.dataflows.symbol_utils import NoMarketDataError
 
@@ -33,9 +33,9 @@ class TestLoadOhlcvNoPoison(unittest.TestCase):
 
     def test_empty_download_raises_and_does_not_cache(self):
         empty = pd.DataFrame()
-        with mock.patch.object(stockstats_utils.yf, "download", return_value=empty) as dl:
-            with self.assertRaises(NoMarketDataError):
-                stockstats_utils.load_ohlcv("FAKE", "2026-01-01")
+        with mock.patch.object(stockstats_utils.yf, "download", return_value=empty), \
+                self.assertRaises(NoMarketDataError):
+            stockstats_utils.load_ohlcv("FAKE", "2026-01-01")
         # Nothing should have been written to the cache.
         self.assertEqual(os.listdir(self._tmp), [])