Add q_gap_threshold to action selection kernel: when greedy Q(best) - Q(flat)
< threshold, default to flat. Teaches model to trade only with conviction.
39D search space (was 38D). Default 0.0 (disabled), hyperopt range [0.0, 0.5].
Remove use_branching parameter from experience_action_select — GPU pipeline
always uses branching DQN. Flat mode was dead code.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>