feat(mq_editor): add iso-contour tracking mode for bass/diffuse regions

trackIsoContour() follows constant energy level through STFT frames
instead of peaks. Useful for broad bass areas where peak detector finds
nothing. Preview in cyan, auto-detects spread on commit (naturally large).

Toggle: ≋ Contour button or C key. Mutually exclusive with ⊕ Explore.

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

1 files changed, 6 insertions, 3 deletions

diff --git a/tools/mq_editor/viewer.js b/tools/mq_editor/viewer.js
index 8f97c3b..c69d9e7 100644
--- a/tools/mq_editor/viewer.js
+++ b/tools/mq_editor/viewer.js
@@ -384,7 +384,9 @@ class SpectrogramViewer {
     const h = this.cursorCanvas.height;
     ctx.clearRect(0, 0, this.cursorCanvas.width, h);
     if (x < 0) return;
-    ctx.strokeStyle = this.exploreMode ? 'rgba(255,160,0,0.8)' : 'rgba(255,60,60,0.7)';
+    ctx.strokeStyle = this.exploreMode === 'contour' ? 'rgba(0,220,220,0.8)'
+                    : this.exploreMode             ? 'rgba(255,160,0,0.8)'
+                    :                               'rgba(255,60,60,0.7)';
     ctx.lineWidth = 1;
     ctx.beginPath();
     ctx.moveTo(x, 0);
@@ -410,11 +412,12 @@ class SpectrogramViewer {
   _drawPreviewPartial(ctx, partial) {
     const curve = partial.freqCurve;
     if (!curve) return;
+    const col = this.exploreMode === 'contour' ? '0,220,220' : '255,160,0';
     ctx.save();
-    ctx.strokeStyle = 'rgba(255,160,0,0.9)';
+    ctx.strokeStyle = `rgba(${col},0.9)`;
     ctx.lineWidth = 2;
     ctx.setLineDash([6, 3]);
-    ctx.shadowColor = 'rgba(255,160,0,0.5)';
+    ctx.shadowColor = `rgba(${col},0.5)`;
     ctx.shadowBlur = 6;
     ctx.beginPath();
     let started = false;