A Rational Scalar-Tilt Target: Late registration of n_s = 27/28

This note late-registers the conditional scalar-tilt target n_s = 27/28 = 0.964285714... and zero running at k_* = 0.05 Mpc^-1. The finite 28-step clock is banked; the HBC radial log-shell lift remains an explicit load-bearing premise. The registration is data-exposed, not blind. The Planck near-match earns zero retrospective credit. The forward test is the first qualifying post-freeze CMB likelihood with materially new data, reproducible posterior products, sigma(n_s) no larger than 0.0025, and an explicit running extension. Support, rational-point falsification, power-law-branch falsification, premise failure and inconclusive outcomes are frozen separately. The deposit includes the PDF, LaTeX source, bibliography, compiled bibliography, machine-readable registration, and source-bound verifier.