lockbox-holdout

The single-touch lockbox — a final anti-overfitting holdout run once, after design freeze, on a window held out from every fold, sweep, and search. Use when finalizing a bakeoff winner before deploy, setting up the A/B/C baselines as OOS bars, or running the S1.5 gate-coherence auto-relax. Covers why looking at the lockbox twice burns it, the lockbox pass conditions, and the three baselines. The lockbox is distinct…