Previously train_baseline_rl.rs only passed commission (tx_cost_bps) to DQN/PPO trainers, ignoring bid-ask spread slippage. Now computes per-fold average spread via spread_cost_bps() (same as evaluate_baseline) and passes total cost (commission + spread) to both trainers. Removes #[allow(dead_code)] — function is now used by all 4 example binaries. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>