fix(mq_editor): destroy old viewer listeners on WAV reload

Each loadAudioBuffer() was creating a new SpectrogramViewer without
removing the previous one's canvas event listeners. Old viewers would
fire on every mouse event, rendering stale spectrogram data and calling
editor.onPartialSelect() with out-of-range indices (hiding the amp panel).

Fix: store handlers as named instance properties, add destroy() to remove
them, and call destroy() before creating a new viewer.

handoff(Claude): bug fix only, no behaviour change
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/tools/mq_editor/app.js b/tools/mq_editor/app.js
index dd0a24f..d53af37 100644
--- a/tools/mq_editor/app.js
+++ b/tools/mq_editor/app.js
@@ -189,6 +189,7 @@ function loadAudioBuffer(buffer, label) {
       });
     }
 
+    if (viewer) viewer.destroy();
     viewer = new SpectrogramViewer(canvas, audioBuffer, stftCache);
     viewer.setFrames(peakFrames);
     document.getElementById('exploreBtn').disabled = false;