feat(mq_editor): replace replicas with harmonics model

- Fundamental f0 always synthesized; harmonics added at n*freq_mult
- decay^n amplitude rolloff per harmonic (capped at 0.90)
- Resonator mode also expanded across harmonics (per-harmonic y1/y2 state)
- UI: h.decay, h.freq (default 2.0), jitter, spread↑/↓ params
- Viewer: faint dotted harmonic bands with spread visualization
- Default freq_mult=2.0 (natural harmonic series)

handoff(Gemini): harmonics model complete, ready for next task

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/tools/mq_editor/utils.js b/tools/mq_editor/utils.js
index ed34b8e..7ab274e 100644
--- a/tools/mq_editor/utils.js
+++ b/tools/mq_editor/utils.js
@@ -55,16 +55,29 @@ function getCanvasCoords(e, canvas) {
 
 // Build upper/lower band point arrays for a frequency curve.
 // factorAbove/factorBelow are fractional offsets (e.g. 0.02 = ±2%).
+// freqMult: optional frequency scaling for harmonics (default 1.0).
 // Returns { upper: [[x,y],...], lower: [[x,y],...] }
-function buildBandPoints(viewer, curve, factorAbove, factorBelow) {
+function buildBandPoints(viewer, curve, factorAbove, factorBelow, freqMult = 1.0) {
   const STEPS = 60;
   const upper = [], lower = [];
   for (let i = 0; i <= STEPS; ++i) {
     const t = curve.t0 + (curve.t3 - curve.t0) * i / STEPS;
     if (t < viewer.t_view_min - 0.01 || t > viewer.t_view_max + 0.01) continue;
-    const f = evalBezier(curve, t);
+    const f = evalBezier(curve, t) * freqMult;
     upper.push([viewer.timeToX(t), viewer.freqToY(f * (1 + factorAbove))]);
     lower.push([viewer.timeToX(t), viewer.freqToY(f * (1 - factorBelow))]);
   }
   return { upper, lower };
 }
+
+// Build center line points at freq * freqMult along the curve.
+function buildCenterPoints(viewer, curve, freqMult = 1.0) {
+  const STEPS = 60;
+  const pts = [];
+  for (let i = 0; i <= STEPS; ++i) {
+    const t = curve.t0 + (curve.t3 - curve.t0) * i / STEPS;
+    if (t < viewer.t_view_min - 0.01 || t > viewer.t_view_max + 0.01) continue;
+    pts.push([viewer.timeToX(t), viewer.freqToY(evalBezier(curve, t) * freqMult)]);
+  }
+  return pts;
+}