Improve Trader V4 training pipeline

Align entry labels with max future edge, tune direction labeling, and harden regression evaluation.

Add training diagnostics, price-plan search, feature screening, and nonlinear benchmark scripts.

training/scripts/04_build_feature_frame.py

@@ -5,7 +5,7 @@ from pathlib import Path
 
 import _bootstrap  # noqa: F401
 from trader_training.features import build_feature_frame
-from trader_training.io_utils import add_common_args, setup_logging
+from trader_training.io_utils import DEFAULT_RAW_ROOT, add_common_args, setup_logging
 
 
 def main() -> None:
@@ -13,6 +13,7 @@ def main() -> None:
     add_common_args(parser)
     parser.add_argument("--replay-path", type=Path)
     parser.add_argument("--split-manifest-path", type=Path)
+    parser.add_argument("--raw-root", type=Path, default=DEFAULT_RAW_ROOT)
     parser.add_argument("--allow-incomplete-days", action="store_true")
     args = parser.parse_args()
     setup_logging()