Sparse trade-completion rewards (98% of bars = 0.0) made mean_reward
always ~0.0, hiding the actual learning signal. Now the GPU monitoring
kernel only accumulates non-zero rewards, giving meaningful per-trade
mean, std, sharpe, and trade count in the epoch summary log.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>