- Add final_sharpe and final_val_loss to TrainingMetrics (last-epoch values)
- Rewrite test_walk_forward_no_overfitting_50_epochs: all checks are relative
to the run's own metrics — no hardcoded thresholds
- Checks: finiteness, gradient health, OOS collapse ratio, IS→OOS gap ratio
- 19/19 smoke tests pass
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>