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/21_benchmark_nonlinear_models.py

@@ -0,0 +1,21 @@
+from __future__ import annotations
+
+import argparse
+import logging
+from pathlib import Path
+
+import _bootstrap  # noqa: F401
+from trader_training.nonlinear_benchmark import benchmark_nonlinear_models
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Run diagnostic nonlinear benchmarks for Direction and Entry.")
+    parser.add_argument("--run-id", required=True)
+    parser.add_argument("--data-root", required=True, type=Path)
+    args = parser.parse_args()
+    logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s event=%(message)s")
+    benchmark_nonlinear_models(args)
+
+
+if __name__ == "__main__":
+    main()