V.P185 — BAO Systematic Improvement NLO→NNLO

Structural improvement: NLO has compounding distance+r_d errors (Ω_m=0.330→shorter distances, r_d=149.04→longer ruler, both push D/r_d down by ~2.3%). NNLO has near-matching Ω_m=0.316 and slight r_d undershoot. Sign flips negative→positive. Same Pareto structure as V.D329.