instrument: deliver continuous playback params live to sounding voices via a seqlock block, holding normalized stage position across time edits

src/shell/instrument/editor_input.cpp

@@ -104,6 +104,13 @@ void ReaSamplerEditor::onMouseUp(int x, int y) {
         invalidate();
         return;
     }
+    // A live control already reached the voices during the drag; its release commits the
+    // final value the same way — no bridge read, no WAV re-decode, no snapshot rebuild.
+    if (dragCommitsLive(kind, paramId)) {
+        commitLive();
+        invalidate();
+        return;
+    }
     // Drag-off delete: releasing a curve-node drag well outside the box removes the dragged
     // point (deletePoint refuses the two endpoints, so an endpoint drag-off is a plain move —
     // its amp keeps the last clamped drag value).