feat: add audio chord detection for spectrogram regions

src/components/piano-roll/PianoRoll.css

@@ -235,6 +235,11 @@
   left: 0;
 }
 
+.piano-roll-toolbar .quant-option.disabled {
+  color: #666;
+  cursor: default;
+}
+
 .piano-roll-automation-toolbar-group {
   display: flex;
   align-items: center;
@@ -408,11 +413,37 @@
 }
 
 .spectrogram-loading-label {
-  padding: 6px 10px;
-  background: rgba(0, 0, 0, 0.6);
-  color: #aaa;
+  min-width: 240px;
+  padding: 10px 12px;
+  background: rgba(0, 0, 0, 0.72);
+  color: #ddd;
   font-size: 11px;
-  border-radius: 3px;
+  border: 1px solid #3a3a3a;
+  border-radius: 6px;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.piano-roll-progress-block {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.piano-roll-progress-track {
+  width: 100%;
+  height: 8px;
+  background-color: #1d1d1d;
+  border: 1px solid #3a3a3a;
+  border-radius: 999px;
+  overflow: hidden;
+}
+
+.piano-roll-progress-fill {
+  height: 100%;
+  background: linear-gradient(90deg, #5a9fd4 0%, #7cc2f1 100%);
+  transition: width 0.15s linear;
 }
 
 .piano-grid-header {