IV.T176 — m_μ/m_e NNLO: k=15/2 at −8.2 ppm (τ-effective, best)

m_μ/m_e = ι_τ^(−124/25)·(1−ι_τ^(15/2)) = 206.7666 at −8.2 ppm from PDG 206.7683 (τ-effective). Structural ID: k = 15/2 = dim(τ³)·W₃(4)/|lobes| = 3·5/2. Numerically 5.3× better than k=23/3 (+43 ppm) and 37.5× better than LO (+307 ppm). The 1/6 = 1/(lobes·sectors) difference between k=23/3 and k=15/2 is a sector-correction. Baryogenesis-lepton duality: same exponent 15 as η_B.