IV.R122 — Structural lifetime estimate

The neutron lifetime formula involves G_F (from electroweak arc), m_e (from mass ratio), Q_beta (from proton-neutron mass difference), all iota_tau-determined. With g_A at +5.5 ppm (IV.T182) and the cancelled form (77 ppm RSS), the structural estimate is promoted to tau-effective. Scope upgraded from conjectural at Wave 46B.