Add rectangle width and height grip editing

src/scene/model/object.rs

@@ -175,6 +175,8 @@ pub enum GripMenuAction {
     Lengthen,
     Radius,
     ArcLength,
+    RectangleWidth,
+    RectangleHeight,
     AddVertex,
     RemoveVertex,
     ConvertToArc,

src/scene/pick/grip.rs

@@ -56,6 +56,8 @@ pub enum GripEditMode {
     Lengthen,
     Radius,
     ArcLength,
+    RectangleWidth,
+    RectangleHeight,
 }
 
 #[derive(Clone, Debug)]
@@ -106,6 +108,18 @@ impl GripEdit {
         edit.mode = GripEditMode::ArcLength;
         edit
     }
+
+    pub fn rectangle_width(handle: Handle, grip_id: usize, world: DVec3) -> Self {
+        let mut edit = Self::single(handle, grip_id, false, world);
+        edit.mode = GripEditMode::RectangleWidth;
+        edit
+    }
+
+    pub fn rectangle_height(handle: Handle, grip_id: usize, world: DVec3) -> Self {
+        let mut edit = Self::single(handle, grip_id, false, world);
+        edit.mode = GripEditMode::RectangleHeight;
+        edit
+    }
 }
 
 // ── Screen-space helpers ───────────────────────────────────────────────────