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_deck.cpp

@@ -107,6 +107,9 @@ void ReaSamplerEditor::dragDeck(int x, int y) {
     // grab. Live feedback; parameter-set commits land on WM_LBUTTONUP.
     (void)x;
     applyDeckKnob(dragParamId_, knobDragValue(dragKnobStartValue_, y - dragStartY_));
+    // A live control is delivered on every move, not only on release — that is the whole
+    // point: the note already sounding tracks the hand on the knob.
+    if (dragCommitsLive(DragKind::kDeckKnob, dragParamId_)) commitLive();
     invalidate();
 }