Replaces stale exp2(am/res) chain description + wrong metrics with the actual
honest state: C=G*LUT(log10(am/res))+W*warp^A, gain=(1-C)*res^rp; dual<=0.72,
fc-scan<=0.59, corpus mean 0.77. Documents the 24-bit metric trap, negative
broadband test, and the remaining structural gaps (combine + FFT-conv, A/B/gamma).