fix(mq_editor): mini-spectrum and spectrogram display improvements

- Fix mini-spectrum: log-scale frequency axis, per-pixel bin averaging,
  red peak bars after extraction
- Fix key handlers swallowing digits in input fields
- Clamp hop size to min 64 to prevent hang
- Store maxDB in STFTCache, use it to normalize both mini-spectrum and
  main spectrogram (fixes clipping at 0dB for pure tones)
- Add Test WAV console validation for 440/660Hz peaks
- Grayscale colormap for main spectrogram

handoff(Gemini): mq_editor display fixes complete, tests not affected

1 files changed, 5 insertions, 0 deletions

diff --git a/tools/mq_editor/fft.js b/tools/mq_editor/fft.js
index 9b9bc94..10a5b45 100644
--- a/tools/mq_editor/fft.js
+++ b/tools/mq_editor/fft.js
@@ -115,6 +115,7 @@ class STFTCache {
 
   compute() {
     this.frames = [];
+    this.maxDB = -Infinity;
     const numFrames = Math.floor((this.signal.length - this.fftSize) / this.hopSize);
 
     for (let frameIdx = 0; frameIdx < numFrames; ++frameIdx) {
@@ -138,10 +139,14 @@ class STFTCache {
         const re = fftOut[i * 2];
         const im = fftOut[i * 2 + 1];
         squaredAmplitude[i] = re * re + im * im;
+        const db = 10 * Math.log10(Math.max(squaredAmplitude[i], 1e-20));
+        if (db > this.maxDB) this.maxDB = db;
       }
 
       this.frames.push({time, offset, squaredAmplitude});
     }
+
+    if (!isFinite(this.maxDB)) this.maxDB = 0;
   }
 
   setHopSize(hopSize) {