Wiring FFT-conv step5 (mask*=win) gives mean 5.2, combine/acc (att/rel from kRTAtt/
kRTRel) gives 4.7 vs base 0.75-0.80 on representative subset. Both belong to the
exp2(mask) structural chain (blend 0.8 + bigkernel) NOT the fitted bridge final-gain.
No code change; bridge + Pchip stays canonical (0.773).