Q-W2v review follow-ups: golden full-blob fixture test, dead-local cleanup, bool-guard static_assert, explicit VelocityCurve qualification

src/shell/instrument/editor_input_browse_zone.cpp

@@ -205,7 +205,6 @@ void ReaSamplerEditor::mouseDownZone(int w, int h, int x, int y) {
     const Rect back = zoneBackRect(w, h);
     if (contains(back, x, y)) { view_ = View::kSample; invalidate(); return; }
     const Rect content = zoneContentArea(w, h);
-    const int pad = 8;
     Rect addR = zoneAddRect(content);
     if (contains(addR, x, y)) {
         // Add a narrow default zone for the picked capture (or the first visible sample as a