V.D233 — sigma-Polarity Neutrino Mass Matrix

The sigma-equivariant 3x3 mass matrix M=[[a,b,0],[b,c,b],[0,b,a]] with a=iota^p, b=iota^q, c=iota^r. Sprint 3 best-fit: p=3.7, q=4.8, r=2.8 giving ratio 32.82 (PDG: 32.58, 0.75%) and Sigma_mnu=0.089 eV. Zero (1,3) entry is structural: winding classes (1,0) and (0,1) on T^2 have no direct coupling; only mixed class mediates. Eigenvalues: lambda_odd=a (sigma-odd, Majorana), lambda_even = (a+c)/2 +/- sqrt((a-c)^2/4+2b^2).