IV.D356 — A-Sector PMNS Rotation: pi-Generator Flavor Rotation on tau^1

Definition: The A-sector (Weak force, pi-generator) propagation on tau^1 induces a flavor-space rotation R on the 3-generation neutrino basis. The sigma-polarity matrices give PMNS = identity (IV.T174); the A-sector adds R_23(theta_A) where sin(theta_A) = 1/(1+iota_tau) approx 0.7455 -> theta_A = 48.2 degrees. Combined with QLC complementarity (IV.T163), this generates large PMNS mixing. Structural origin: pi-generator lobe structure on L = S^1 v S^1 mixes the (nu_mu, nu_tau) states via the chi_+/chi_- lobe modes.