fix(memory): gate past-context lessons to point-in-time in backtests

- get_past_context returned every resolved lesson regardless of the run date, so
  a historical run could learn from an outcome that had not happened yet
- record each resolved entry's resolution date (the last price bar used) and
  filter get_past_context(as_of=trade_date) on it for a historical run; a
  current-date run passes None so live behavior and pre-migration entries (no
  stored resolution date, conservatively excluded from backtests) are unaffected #1251

tests/test_symbol_normalization_paths.py

@@ -41,18 +41,21 @@ def test_fetch_returns_normalizes_symbol(monkeypatch):
             queried.append(symbol)
 
         def history(self, *args, **kwargs):
-            return pd.DataFrame({"Close": [100.0, 101.0, 102.0, 103.0, 104.0, 105.0, 106.0]})
+            prices = [100.0, 101.0, 102.0, 103.0, 104.0, 105.0, 106.0]
+            idx = pd.date_range(start="2025-01-02", periods=len(prices), freq="D")
+            return pd.DataFrame({"Close": prices}, index=idx)
 
     monkeypatch.setattr(tg.yf, "Ticker", FakeTicker)
 
     # _fetch_returns does not use ``self``; call unbound to avoid building the graph.
-    raw, alpha, days = TradingAgentsGraph._fetch_returns(
+    raw, alpha, days, resolved = TradingAgentsGraph._fetch_returns(
         None, "XAUUSD", "2025-01-02", holding_days=5, benchmark="SPY"
     )
 
     assert queried[0] == "GC=F"  # stock symbol normalized (#984)
     assert queried[1] == "SPY"   # benchmark left as the canonical symbol
     assert raw is not None and days is not None
+    assert resolved == "2025-01-07"  # resolution date recorded (#1251)
 
 
 def test_news_lookup_normalizes_symbol(monkeypatch):