New test coverage for 3 previously untested GPU training paths:
- hyperopt.rs: test_hyperopt_preloaded_data, test_hyperopt_shared_data,
test_hyperopt_paths_consistent — exercises train_with_preloaded_data and
train_with_shared_data which bypass walk-forward (direct train_with_data_full_loop)
- walk_forward.rs: test_walk_forward_multi_fold — tight fractions (0.3/0.1/0.1/0.1)
to guarantee 2+ folds, validating reset_for_fold, graph_aux invalidation, and
CUDA graph survival across fold boundaries
- regression.rs: test_no_hang_single_epoch (VRAM oversubscription guard),
test_counterfactual_experiences_in_buffer (silent data loss guard),
test_gpu_n_episodes_config_honored (auto-scaling removal guard)
Also fixes: unclosed for-loop brace in gpu_per_integration_test.rs (pre-existing)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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