feat(mq_editor): E key for extract, style cleanup, doc update

- Map 'E' key to Extract Partials
- Move extractBtn inline style to CSS rule #extractBtn
- Hoist autoSpreadAllBtn DOM ref to top with other refs
- Drop unused PADY local var in _renderAmpEditor
- Remove redundant comment before extractBtn listener
- README: add E/Esc keys, add editor.js to architecture, mark Phase 3 done

handoff(Gemini): mq_editor UX polish + doc consolidated
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

3 files changed, 15 insertions, 6 deletions

diff --git a/tools/mq_editor/README.md b/tools/mq_editor/README.md
index 4250d33..141963a 100644
--- a/tools/mq_editor/README.md
+++ b/tools/mq_editor/README.md
@@ -35,14 +35,17 @@ open tools/mq_editor/index.html
 |-----|--------|
 | `1` | Play synthesized audio |
 | `2` | Play original audio |
+| `E` | Extract Partials |
 | `P` | Toggle raw peak overlay |
 | `A` | Toggle mini-spectrum: original ↔ synthesized |
+| `Esc` | Deselect partial |
 | Shift+scroll | Zoom time axis |
 | Scroll | Pan time axis |
 
 ## Architecture
 
-- `index.html` — UI, playback, extraction orchestration
+- `index.html` — UI, playback, extraction orchestration, keyboard shortcuts
+- `editor.js` — Property panel and amplitude bezier editor for selected partials
 - `fft.js` — Cooley-Tukey radix-2 FFT + STFT cache
 - `mq_extract.js` — MQ algorithm: peak detection, forward tracking, backward expansion, bezier fitting
 - `mq_synth.js` — Oscillator bank synthesis from extracted partials
@@ -83,7 +86,12 @@ open tools/mq_editor/index.html
   - [x] Replica oscillator bank (spread, jitter, phase integration)
   - [x] Synthesis debug checkboxes (disable jitter/spread)
   - [x] Synthesized STFT cache for FFT comparison
-- [ ] Phase 3: Editing UI (drag control points, replicas)
+- [x] Phase 3: Editing UI
+  - [x] Partial selection with property panel (freq/amp/synth tabs)
+  - [x] Amplitude bezier drag editor
+  - [x] Synth params with jog sliders (decay, jitter, spread)
+  - [x] Auto-spread detection per partial and global
+  - [x] Mute / delete partials
 - [ ] Phase 4: Export (.spec + C++ code generation)
 
 ## See Also
diff --git a/tools/mq_editor/editor.js b/tools/mq_editor/editor.js
index b767534..157186a 100644
--- a/tools/mq_editor/editor.js
+++ b/tools/mq_editor/editor.js
@@ -275,7 +275,6 @@ class PartialEditor {
     const canvas = this._ampCanvas;
     const ctx    = this._ampCtx;
     const W = canvas.width, H = canvas.height;
-    const PADY = 10;
 
     // Sync time range with viewer
     const amp  = this._amp;
diff --git a/tools/mq_editor/index.html b/tools/mq_editor/index.html
index fa7543c..f6d052b 100644
--- a/tools/mq_editor/index.html
+++ b/tools/mq_editor/index.html
@@ -40,6 +40,7 @@
     }
     button:hover { background: #4a4a4a; }
     button:disabled { opacity: 0.5; cursor: not-allowed; }
+    #extractBtn { background: #666; color: #fff; font-weight: bold; border-color: #888; }
     input[type="file"] { display: none; }
     .params {
       display: inline-block;
@@ -356,6 +357,7 @@
     const wavFile = document.getElementById('wavFile');
     const chooseFileBtn = document.getElementById('chooseFileBtn');
     const extractBtn = document.getElementById('extractBtn');
+    const autoSpreadAllBtn = document.getElementById('autoSpreadAllBtn');
     const playBtn = document.getElementById('playBtn');
     const stopBtn = document.getElementById('stopBtn');
     const canvas = document.getElementById('canvas');
@@ -512,14 +514,11 @@
       }, 50);
     }
 
-    // Extract partials
     extractBtn.addEventListener('click', () => {
       if (!audioBuffer) return;
       runExtraction();
     });
 
-    // Auto-spread all partials
-    const autoSpreadAllBtn = document.getElementById('autoSpreadAllBtn');
     autoSpreadAllBtn.addEventListener('click', () => {
       if (!extractedPartials || !stftCache) return;
       const fs = stftCache.fftSize;
@@ -642,6 +641,9 @@
           viewer.showSynthFFT = !viewer.showSynthFFT;
           viewer.renderSpectrum();
         }
+      } else if (e.code === 'KeyE') {
+        e.preventDefault();
+        if (!extractBtn.disabled) extractBtn.click();
       } else if (e.code === 'Escape') {
         if (viewer) viewer.selectPartial(-1);
       }