fix: close review findings on spline EGs — engine, codec, and popup/overlay UI grammar

Live pitch depth, Gate/Spline enable-rule agreement, inert kTrigLength, NaN wire guards, hard-flag-tail corruption no longer wipes the record, RT/cold spline tie-break, retired alt-click, marker-shadow fix, plus new test coverage.

src/shell/instrument/editor_models.cpp

@@ -112,15 +112,6 @@ void ReaSamplerEditor::unpackEnvelope(OverlayEnv which, const StageEnvelope& env
     }
 }
 
-instrument::ui::DeckEnableState ReaSamplerEditor::deckEnableState() const {
-    const PlaySeconds& play = params_.play;
-    return instrument::ui::DeckEnableState{
-        play.pitchEnv.enabled, play.filter.enabled,
-        play.ampSpline.mode == EnvMode::Spline,
-        play.pitchSpline.mode == EnvMode::Spline,
-        play.filterSpline.mode == EnvMode::Spline};
-}
-
 const VelocityCurve& ReaSamplerEditor::splineFor(OverlayEnv which) const {
     switch (which) {
         case OverlayEnv::kPitch:  return params_.play.pitchSpline.contour;
@@ -177,12 +168,4 @@ VelocityCurve& ReaSamplerEditor::editedCurve() {
     return curveFor(curvePopup_);
 }
 
-void ReaSamplerEditor::closeCurvePopup() {
-    curvePopup_ = CurveTarget::kNone;
-    if (drag_ == DragKind::kCurveNode) {
-        drag_ = DragKind::kNone;
-        curvePointIndex_ = -1;
-    }
-}
-
 }  // namespace reasampler::vst