chore: remove code nothing uses

- is_yahoo_safe, has_checkpoint, get_wall_times, the graph's curr_state and the project_dir config key
- the CLI's final_report and current_agent state, its duplicate get_analysis_date and the save_report_to_disk wrapper
- the dotenv import guard (a hard dependency) and a warning filter for langgraph-checkpoint 4.0.3

tests/test_symbol_utils.py

@@ -7,7 +7,6 @@ import pytest
 from tradingagents.dataflows.symbol_utils import (
     NoMarketDataError,
     crypto_base,
-    is_yahoo_safe,
     normalize_symbol,
 )
 
@@ -88,17 +87,6 @@ class TestNoMarketDataError(unittest.TestCase):
         self.assertEqual(err.canonical, "FOOBAR")
 
 
-@pytest.mark.unit
-class TestIsYahooSafe(unittest.TestCase):
-    def test_accepts_structural_chars(self):
-        for sym in ("AAPL", "GC=F", "^GSPC", "BRK.B", "BTC-USD"):
-            self.assertTrue(is_yahoo_safe(sym))
-
-    def test_rejects_slash_and_space(self):
-        for sym in ("a/b", "AA PL", ""):
-            self.assertFalse(is_yahoo_safe(sym))
-
-
 @pytest.mark.unit
 class TestCryptoBase(unittest.TestCase):
     def test_resolves_known_crypto_forms(self):