S-VIEW-10: velocity-curve editor UI — draggable spline box beside the Sample hero + in the Zone panel, all math through the pure velocity_curve module

src/vst/velocity_curve.h

@@ -133,6 +133,22 @@ public:
     // for determinism (mirror of nodeAtPoint).
     int pointAtPixel(const Box& box, int x, int y) const;
 
+    // A node's drawn pixel position (S-VIEW-10). The ONE point->pixel mapping — the same mapping
+    // pointAtPixel hit-tests against — exposed so the editor shell draws the trace + node handles
+    // at exactly the coordinates the hit-test expects (draw and grab can never drift).
+    struct CurvePixel {
+        int x = 0;
+        int y = 0;
+    };
+    static CurvePixel pixelFromPoint(const Box& box, const VelocityPoint& p);
+
+    // The absolute pixel -> (velocity, amp) inverse (S-VIEW-10): where an empty-space click lands
+    // as a NEW control point, box-clamped. The exact inverse of pixelFromPoint's mapping (within
+    // the one-pixel quantum), so an added point appears under the cursor. Degenerate box: a
+    // zero-width box reads velocity 0; a height <= 1 box reads amp 1 (the top row), mirroring
+    // pixelFromPoint's degenerate collapse.
+    static VelocityPoint pointFromPixel(const Box& box, int x, int y);
+
     // Resolve a drag of point `index` by a pixel delta since grab, given the curve AS OF GRAB TIME
     // (`grabCurve` — the shell snapshots it on mouse-down so the delta is absolute) and the box.
     // Maps the pixel delta to a (velocity, amp) delta over the box, then applies movePoint's clamp