V.D238 — SA-i mod-W₃(4) Baryogenesis Mechanism: ι_τ¹⁵ = (ι_τ³)^W₃(4)

Wave 12 upgrade: SA-i mod-5 baryogenesis mechanism with proof-carrying structures. ι_τ¹⁵ = (ι_τ³)^W₃(4) from 5 generator winding sectors. Exponent uniqueness (3×5=15 unique structural factorization), coefficient (5/6) uniquely forced from threshold counting. Sakharov conditions formalized as Nat fields. Scope: τ-effective.