IV.T151 — Higgs Mass Sub-1000 ppm Formula via Window Universality

The Higgs-to-neutron mass ratio is m_H/m_n = (4 - iota_tau^3 / (1 - W_3(4)*kappa_omega)) / kappa_omega = (4 - iota_tau^3/(1 - 5*kappa_omega)) / kappa_omega = 133.372, compared to PDG m_H/m_n = 133.306, a deviation of +493 ppm. Scope is tau-effective: the correction denominator (1 - 5*kappa_omega) uses W_3(4) = 5, the same window value that governs all three EW NLO corrections (IV.T140, Wave 1A). The formula extends the base (4 - iota_tau^3)/kappa_omega at +2244 ppm by the natural NLO correction via Window Universality. Bonus (conjectural): n=6 gives (4 - iota_tau^3/(1 - 6*kappa_omega))/kappa_omega = 133.315 at +68 ppm; structural meaning of coefficient 6 remains open (see IV.R399).