instrument: fix AHD node-tracking/tie-break/live-latch defects and close staged-envelope-curve test gaps

src/shell/instrument/editor_paint_deck.cpp

@@ -111,7 +111,11 @@ void ReaSamplerEditor::paintDeck(LICE_IBitmap* bmp, const FaceLayout& fl) {
         // The overlay-select radio: filled in the tertiary accent (the colour the overlay
         // traces in) when this group's envelope is the one on the waveform, hollow otherwise.
         if (g.captionRadio.id >= 0) {
-            const bool on = (overlayEnv_ == overlayEnvForRadio(g.captionRadio.id));
+            // overlayEnvForRadio returns kNone for BOTH "not a radio id" and "no selection" —
+            // a non-radio id must never read as lit just because nothing is selected, so the
+            // picked env has to be checked against kNone itself, not just matched by equality.
+            const OverlayEnv picked = overlayEnvForRadio(g.captionRadio.id);
+            const bool on = picked != OverlayEnv::kNone && overlayEnv_ == picked;
             const bool hov = isHovered(HoverKind::kEnvRadio, g.captionRadio.id);
             const Rect& rb = g.captionRadio.box;
             LICE_DrawRect(bmp, rb.x, rb.y, rb.width - 1, rb.height - 1,