Critical bug: all 3 DQN action selection methods (select_action,
select_action_with_confidence, select_action_inference) used
FactoredAction::from_index() which maps indices 0-4 to exposure_idx=0
(Short100) via division by 9. This is the root cause of action
diversity collapse during both training and production inference.
Fix: ExposureLevel::from_index() + OrderRouter::route_default() in all
DQN paths. Also fixes hyperopt objective thresholds (<10 → <3 for
5-action degenerate detection), stale defaults/comments, integration
test configs.
Files: dqn.rs (3 methods), trainer.rs (validation + select_action),
hyperopt/adapters/dqn.rs (thresholds), dqn_model.rs (comments),
train_baseline_rl.rs (default), reward.rs (comment),
dqn_integration.rs + ensemble_integration.rs (num_actions).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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