feat(mq_editor): switch curve interpolation to Lagrange through all control points

Replace cubic Bezier with Lagrange interpolation so P1/P2 are actual
points on the curve. Eval uses stored t1/t2 as arbitrary knot positions.
fitBezier keeps least-squares but with Lagrange basis at u=1/3,2/3.
Remove endpoint companion drag (no longer tangent handles).
TODO: support arbitrary number of inner control points.

handoff(Claude): Lagrange interpolation replaces Bezier in mq_editor curve eval/fit.

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

1 files changed, 2 insertions, 13 deletions

diff --git a/tools/mq_editor/editor.js b/tools/mq_editor/editor.js
index 0854ec0..a7d0879 100644
--- a/tools/mq_editor/editor.js
+++ b/tools/mq_editor/editor.js
@@ -25,8 +25,7 @@ class PartialEditor {
 
     // Private state
     this._selectedIndex  = -1;
-    this._dragPointIndex    = -1;
-    this._dragCompanionOff  = null; // {dt, dv} offset of companion handle relative to anchor
+    this._dragPointIndex = -1;
     this._amp = { tMin: 0, tMax: 1, ampTop: 1 };
 
     this._setupButtons();
@@ -496,12 +495,7 @@ class PartialEditor {
       for (let i = 0; i < 4; ++i) {
         if (Math.hypot(this._tToX(curve['t' + i]) - x, this._ampToY(curve['a' + i]) - y) <= 8) {
           if (this.onBeforeChange) this.onBeforeChange();
-          this._dragPointIndex   = i;
-          this._dragCompanionOff = null;
-          if (i === 0)
-            this._dragCompanionOff = { da: curve.a1 - curve.a0 };
-          else if (i === 3)
-            this._dragCompanionOff = { da: curve.a2 - curve.a3 };
+          this._dragPointIndex = i;
           canvas.style.cursor  = 'grabbing';
           e.preventDefault();
           return;
@@ -516,11 +510,6 @@ class PartialEditor {
         const curve = this.partials[this._selectedIndex].freqCurve;
         const i     = this._dragPointIndex;
         curve['a' + i] = Math.max(0, this._yToAmp(y));
-        if (this._dragCompanionOff) {
-          const off = this._dragCompanionOff;
-          if (i === 0) { curve.a1 = curve.a0 + off.da; }
-          else          { curve.a2 = curve.a3 + off.da; }
-        }
         this._renderAmpEditor();
         if (this.viewer) this.viewer.render();
         e.preventDefault();