Systematics isolated: Pchip LUT frozen cap under-predicts loud tail (t1k_b1f needs
LUT 0.70 at xv 0.85), over-predicts low tail (al lv24 needs 0.35 at xv -0.5).
Real LUT extracted from refs; parametric fit A=-13.78/B=68.29/g=0.344 regresses dual
(rejects in full render). Structural next: decode BandConfig ctx+0x188 writers.