Threads b_logits_dir (= exp_b_logits, first N*b0*NA region for direction
branch), per_sample_support, atom_positions (NULL = linear), and n_atoms
through experience_action_select kernel launch in gpu_experience_collector.
After amendment commit 5de5e546a, the kernel uses single-distribution C51
Thompson with production's adaptive per-direction support — no IQN
inference required at rollout.
Plan C Task 3 (corrected file path: collector, not trainer per
gpu_dqn_trainer.rs/gpu_experience_collector.rs distinction).
380d0ac0d3