fix: filter NaN in max(), remove redundant ternary, handle non-finite vbt results

rdagent/components/backtesting/backtest_engine.py

@@ -222,7 +222,7 @@ class FactorBacktester:
 
             # Calculate return for this step
             if step > 0:
-                prev_price = float(price_values[step - 1]) if step > 0 else current_price
+                prev_price = float(price_values[step - 1])
                 if prev_price > 0:
                     step_return = (current_price - prev_price) / prev_price * position
                     returns_history.append(step_return)

rdagent/components/backtesting/vbt_backtest.py

@@ -83,7 +83,8 @@ def _cross_check_with_vbt(
             init_cash=10_000.0,
             freq=freq,
         )
-        return float(pf.total_return())
+        tr = float(pf.total_return())
+        return tr if np.isfinite(tr) else None
     except Exception:
         return None