CDN-219: The Holdout Request Ledger

CDN-219 converts the CDN-218 c/f blockage into an actionable public-asset ledger. The current public record contains ten Agol c/f timings, 7534 published full-fit forecast rows, and five external GO-6456 b/d/e timing checks. It does not contain the decisive public assets: per-transit leave-one-out forecasts/residuals or reproducible notebook/code, plus an independent c/f timing row with frozen forecast comparison and no fit reuse. The audit is actionable, but TTY is not paid.