Walk-forward evaluation was using the final epoch model, which may have
overfit. Now loads the best per-epoch Sharpe checkpoint (saved during
training) back into the agent before running the walk-forward backtest.
Trial 0 showed Sharpe +3.30 at epoch 2 vs +1.84 at epoch 8 (final).
The walk-forward should evaluate the peak model, not the final one.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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