fix: close review findings on the velocity-curve deck and bipolar curves

Cancels the curve-node drag whenever the popup closes so Esc mid-drag can't alias the amp curve; generalizes CurveTarget routing to one switch; fixes stale/overstated comments; clamps a pre-v12 depth fold; adds deck-inertness and filter-fold test coverage.

src/shell/instrument/editor_paint_chrome.cpp

@@ -1,7 +1,7 @@
 // editor_paint_chrome.cpp — the CHROME band's painter: the toolbar row (product title +
-// live readout, then the control run — preview, preview-velocity knob, curve button,
-// Mono|Stereo, Browse) over the strip row, which the piano strip has to itself. Windows-only;
-// all rects come from the pure sample_chrome interior and the pure keyboard_strip geometry.
+// live readout, then the control run — preview, preview-velocity knob, Mono|Stereo, Browse)
+// over the strip row, which the piano strip has to itself. Windows-only; all rects come from
+// the pure sample_chrome interior and the pure keyboard_strip geometry.
 
 #include "shell/instrument/reasampler_editor.h"
 
@@ -140,8 +140,9 @@ void ReaSamplerEditor::paintChrome(LICE_IBitmap* bmp, const FaceLayout& fl, bool
         drawButton(bmp, box, nullptr, st, /*warn=*/false);
         const PreviewGlyph g = previewGlyph(cr.preview);
         if (!g.empty()) {
-            const LICE_pixel ink =
-                toLice(roleColor(active ? Role::BgBase : Role::TextPrimary));
+            // Same surface as the button label, so the glyph tracks drawButton's own rule
+            // (buttonLabelRole) rather than a second copy of it that could desync from the kit.
+            const LICE_pixel ink = toLice(roleColor(buttonLabelRole(st)));
             LICE_FillTriangle(bmp, g.leftX, g.topY, g.leftX, g.bottomY, g.apexX, g.apexY,
                               ink, 1.0f, 0);
         }