Add editor/gain_curve.rs: a square panel beside the scrolling plot showing the
channel transfer (out vs in, -60..0 dB) for whichever channel the plot tab
selects. Plots the full wet path — out = (in + pre_gain) + gain_reduction + makeup
— using the shared Compressor::gain_computer (now pub) so it matches the DSP and
the GR meter. Unity-reference diagonal + threshold marker; mix not folded in.
Update README structure/status to reflect the editor/ widget module and the
completed Stage 6 visualisers.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Mikkeli Matlock