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_waveform.cpp

@@ -78,6 +78,9 @@ void ReaSamplerEditor::dragWaveform(const FaceLayout& fl, int x, int y) {
         const AmpEnvelope edited = resolveNodeDrag(dragStartEnv_, envNode_, overlay, totalSeconds,
                                                    envClampBounds(), dx, y - dragStartY_);
         unpackEnvelope(edited, frames, dragStartFrame_, params_.play);
+        // In Gate the node IS a live AHDSR control, so the sounding note follows the drag;
+        // Trigger's nodes rewrite the play span and still commit on release.
+        if (dragCommitsLive(DragKind::kEnvNode)) commitLive();
         invalidate();  // live feedback; commit on WM_LBUTTONUP
         return;
     }