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_controls.cpp

@@ -11,12 +11,10 @@
 #include <cstdint>
 #include <cstdio>   // snprintf (deck value labels)
 #include <string>
-#include <utility>  // std::as_const (the const/non-const editedCurve pair)
 #include <vector>
 
 #include "core/instrument/engine/filter/filter_params.h"  // the filter's own control laws
 #include "core/instrument/engine/master_gain.h"  // master-gain dB<->linear<->knob taper
-#include "core/instrument/map/trigger_seam.h"    // triggerPlayLength (the Trigger play span)
 #include "core/instrument/ui/deck_groups.h"      // sampleDeckGroups (the deck's composition)
 #include "core/instrument/ui/knob_deck.h"        // deckHeight / kDeckKnobSize (the band's own height)
 #include "core/util/clamp01.h"
@@ -26,7 +24,7 @@
 
 namespace reasampler::vst {
 
-using namespace reasampler::instrument::map;  // PlaySeconds vocabulary + trigger_seam
+using namespace reasampler::instrument::map;  // PlaySeconds vocabulary
 using instrument::ui::computeSampleBands;
 using instrument::ui::chromeRects;
 using instrument::ui::deckHeight;
@@ -299,6 +297,15 @@ double ReaSamplerEditor::deckControlNorm(int id) const {
     }
 }
 
+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};
+}
+
 void ReaSamplerEditor::applyDeckKnob(int id, double norm) {
     if (!processor_) return;
     norm = clamp01(norm);