One taper, one modifier law: extract param_taper, raise the stage ceiling to 10 s, and make the AHDSR schematic axis the taper itself

src/shell/instrument/editor_internal.h

@@ -15,6 +15,7 @@
 #include "core/instrument/map/sample_map.h"         // SampleChoice / SampleRefs (sampleLabel)
 #include "core/instrument/ui/editor_geometry.h"     // Rect (the shared sub-rect type)
 #include "core/instrument/ui/keyboard_strip.h"      // noteName (the one note-naming source)
+#include "core/instrument/ui/param_taper.h"         // DragModifiers (the shared interaction law)
 
 #ifdef _WIN32
 #include "wdltypes.h"
@@ -70,6 +71,15 @@ inline std::string sampleLabel(const std::vector<instrument::map::SampleChoice>&
 
 #ifdef _WIN32
 
+// THE modifier read, for every drag surface and every gesture resolver. One helper so the editor
+// cannot grow a second modifier grammar. GetKeyState rather than WM_MOUSEMOVE's wParam because a
+// modifier can be pressed or released with the mouse standing still, and the re-anchor has to see
+// that on the next move it does get.
+inline instrument::ui::DragModifiers dragModifiers() {
+    return instrument::ui::DragModifiers{(GetKeyState(VK_SHIFT) & 0x8000) != 0,
+                                         (GetKeyState(VK_CONTROL) & 0x8000) != 0};
+}
+
 // The editor's own sub-rect type is `Rect` (editor_geometry); the kit draws against
 // `KitBox` (component_geometry). This is the single boundary that bridges them so every
 // draw routes through the shared kit (theme roles + draw_kit).