IV.T174 — θ₂₃ NLO via Window Algebra at +8604 ppm

sin(θ₂₃) = 1/(1+ι_τ)·(1−ι_τ⁵) gives sin²θ₂₃=0.5507 at +8604 ppm from PDG 0.546. Wave 11A: A-sector rotation mechanism established — the π-generator acts on base cycle g₃ with rotation angle sin(θ_A)=ι_τ/(1+ι_τ)=κ_ω. LO: sin(θ₂₃)=1/(1+ι_τ); NLO: Window factor (1−ι_τ⁵). W₃(4)=5 universally governs NLO.