fix(mq_editor): fuse spread_above/below into single spread param

Asymmetric spread offset the pitch center. Replace with a single
symmetric `spread` in harmonics config. autodetectSpread now returns
max(above, below). Update all defaults, UI, comments, and README.

handoff(Gemini): spread is now a single param; no compat shims.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 7 insertions, 9 deletions

diff --git a/tools/mq_editor/app.js b/tools/mq_editor/app.js
index d54e5f3..380bb12 100644
--- a/tools/mq_editor/app.js
+++ b/tools/mq_editor/app.js
@@ -231,10 +231,9 @@ function loadAudioBuffer(buffer, label) {
     viewer.onExploreCommit = (partial) => {
       if (!extractedPartials) extractedPartials = [];
       pushUndo();
-      const {spread_above, spread_below} = autodetectSpread(partial, stftCache, fftSize, audioBuffer.sampleRate);
-      if (!partial.harmonics) partial.harmonics = { decay: 0.0, freq_mult: 2.0, jitter: 0.05, spread_above: 0.02, spread_below: 0.02 };
-      partial.harmonics.spread_above = spread_above;
-      partial.harmonics.spread_below = spread_below;
+      const {spread} = autodetectSpread(partial, stftCache, fftSize, audioBuffer.sampleRate);
+      if (!partial.harmonics) partial.harmonics = { decay: 0.0, freq_mult: 2.0, jitter: 0.05, spread: 0.02 };
+      partial.harmonics.spread = spread;
       extractedPartials.unshift(partial);
       refreshPartialsView(0);
       setStatus(`${exploreMode}: added partial (${extractedPartials.length} total)`, 'info');
@@ -345,7 +344,7 @@ function createNewPartial() {
       v0: 440,     v1: 440,         v2: 440,          v3: 440,
       a0: 1.0,     a1: 1.0,         a2: 1.0,          a3: 1.0,
     },
-    harmonics: { decay: 0.0, freq_mult: 2.0, jitter: 0.05, spread_above: 0.02, spread_below: 0.02 },
+    harmonics: { decay: 0.0, freq_mult: 2.0, jitter: 0.05, spread: 0.02 },
   };
   extractedPartials.unshift(newPartial);
   refreshPartialsView(0);
@@ -369,12 +368,11 @@ function autoSpreadAll() {
   if (!extractedPartials || !stftCache) return;
   const fs = stftCache.fftSize;
   const sr = audioBuffer.sampleRate;
-  const defaults = { decay: 0.0, freq_mult: 2.0, jitter: 0.05, spread_above: 0.02, spread_below: 0.02 };
+  const defaults = { decay: 0.0, freq_mult: 2.0, jitter: 0.05, spread: 0.02 };
   for (const p of extractedPartials) {
-    const {spread_above, spread_below} = autodetectSpread(p, stftCache, fs, sr);
+    const {spread} = autodetectSpread(p, stftCache, fs, sr);
     if (!p.harmonics) p.harmonics = { ...defaults };
-    p.harmonics.spread_above = spread_above;
-    p.harmonics.spread_below = spread_below;
+    p.harmonics.spread = spread;
   }
   if (viewer) viewer.render();
   const sel = viewer ? viewer.selectedPartial : -1;