fix: draw color picker handle on top of gradient

src/widget/color_picker/mod.rs

@@ -606,6 +606,14 @@ where
             (1.0 - self.active_color.value).mul_add(bounds.height, bounds.position().y)
                 - handle_radius,
         );
+        renderer.with_layer(
+            Rectangle {
+                x,
+                y,
+                width: handle_radius.mul_add(2.0, 1.0),
+                height: handle_radius.mul_add(2.0, 1.0),
+            },
+            |renderer| {
                 renderer.fill_quad(
                     Quad {
                         bounds: Rectangle {
@@ -640,6 +648,8 @@ where
                     },
                     Color::TRANSPARENT,
                 );
+            },
+        );
     }
 
     fn overlay<'b>(