fix(mq_editor): correct phaseInterp quadratic coefficient and stale phase prediction

- phaseInterp: missing *0.5 on quadratic term made interpolated phase 2x off
- trackPartials: phase advance now scaled by (age+1) to cover frames missed
  during a partial gap, preventing stale predictions after consecutive misses

handoff(Claude): two bugs fixed in mq_extract.js phase tracking

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

1 files changed, 4 insertions, 2 deletions

diff --git a/tools/mq_editor/mq_extract.js b/tools/mq_editor/mq_extract.js
index a530960..c084b43 100644
--- a/tools/mq_editor/mq_extract.js
+++ b/tools/mq_editor/mq_extract.js
@@ -40,7 +40,7 @@ function phaseInterp(p_minus, p_center, p_plus, p_frac) {
   while (dp_plus > Math.PI) dp_plus -= 2 * Math.PI;
   while (dp_plus < -Math.PI) dp_plus += 2 * Math.PI;
   
-  const p_interp = p_center + (dp_plus - dp_minus) * p_frac * 0.5 + (dp_plus + dp_minus) * p_frac * p_frac;
+  const p_interp = p_center + (dp_plus - dp_minus) * p_frac * 0.5 + (dp_plus + dp_minus) * 0.5 * p_frac * p_frac;
   return p_interp;
 }
 
@@ -130,7 +130,8 @@ function trackPartials(frames, params) {
       const predictedFreq = lastFreq + velocity;
       
       // Predict phase for the current frame based on the last frame's frequency.
-      const phaseAdvance = 2 * Math.PI * lastFreq * hopSize / sampleRate;
+      // Multiply by (age+1) to account for frames missed during a gap.
+      const phaseAdvance = 2 * Math.PI * lastFreq * (partial.age + 1) * hopSize / sampleRate;
       const predictedPhase = lastPhase + phaseAdvance;
       
       const tol = Math.max(predictedFreq * trackingRatio, minTrackingHz);
@@ -170,6 +171,7 @@ function trackPartials(frames, params) {
       const velocity = cand.velocity || 0;
       const predictedFreq = lastFreq + velocity;
 
+      // Candidates die on first miss so age is always 0 here, but kept consistent.
       const phaseAdvance = 2 * Math.PI * lastFreq * hopSize / sampleRate;
       const predictedPhase = lastPhase + phaseAdvance;