V.T189 — Grid Optimum Structural Derivation: (203/175, 609/700)

Grid optimum (Δpq,Δpr)=(1.16,0.87) is exactly (8/7+3/175, 6/7+9/700)=(203/175, 609/700). The structural derivation uses only dim(τ³)=3, lobes=2, sectors=3, n=7=2×lobes+sectors, W₃(4)=5. Mass ratio Δm²₃₁/Δm²₂₁=32.577 at +18.5 ppm from PDG.