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/18_diagnose_training_run.py

@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+import argparse
+
+import _bootstrap  # noqa: F401
+from trader_training.diagnostics import diagnose_training_run
+from trader_training.io_utils import add_common_args, setup_logging
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    add_common_args(parser)
+    args = parser.parse_args()
+    setup_logging()
+    diagnose_training_run(args)
+
+
+if __name__ == "__main__":
+    main()