fix: replace unicode chars that break Windows cp1252 encoding

ml_engine/train_and_backtest.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 """
-BTC ML Trading Strategy — Train & Backtest Engine
+BTC ML Trading Strategy -- Train & Backtest Engine
 Self-contained script that runs on the Windows PC with GPU.
 
 Usage:
@@ -280,7 +280,7 @@ def walk_forward_train_test(df: pd.DataFrame, feature_cols: list, config: dict)
         try:
             model.fit(X_train, y_train)
         except Exception as e:
-            print(f"  Window {w+1}: training failed — {e}", file=sys.stderr)
+            print(f"  Window {w+1}: training failed -- {e}", file=sys.stderr)
             continue
 
         # Get predictions on test set
@@ -492,7 +492,7 @@ def compile_results(trades: list, per_window_sharpe: list,
 # ---------------------------------------------------------------------------
 
 def main():
-    parser = argparse.ArgumentParser(description="BTC ML Trading — Train & Backtest")
+    parser = argparse.ArgumentParser(description="BTC ML Trading -- Train & Backtest")
     parser.add_argument("--config", required=True, help="Path to config JSON")
     parser.add_argument("--data", required=True, help="Path to OHLCV CSV")
     parser.add_argument("--output", required=True, help="Path to output results JSON")
@@ -505,7 +505,7 @@ def main():
     # Load data
     print(f"Loading data from {args.data}...")
     df = pd.read_csv(args.data, parse_dates=["timestamp"])
-    print(f"  {len(df)} rows, {df['timestamp'].iloc[0]} → {df['timestamp'].iloc[-1]}")
+    print(f"  {len(df)} rows, {df['timestamp'].iloc[0]} -> {df['timestamp'].iloc[-1]}")
 
     # Compute features
     print("Computing features...")