editor: scale gizmo fully self-drawn (screen-space, view-independent)

ImGuizmo scale hover/drag relies on ray-plane intersection with the
axis as plane normal; in front views (axis ⟂ camera-to-object) the
intersection numerator is identically zero, so handles can't be
grabbed and values jump randomly; axes parallel to the view have zero
screen displacement. Submodule is read-only and AxisMask can only hide
degenerate axes, not replace them.

Replace the library scale path entirely with a screen-space gizmo:
- three axis rods (line + end square) + center uniform-scale square,
  constant screen size in any view
- axis drag: mouse delta projected onto the axis' screen direction
- axis pointing at camera: radial mapping (drag away = grow)
- center square: uniform scale (library MT_SCALE_XYZ semantics)
- Ctrl snapping quantizes the result; scale clamped >= 0.01
- pick suppressed while hovering/dragging the self-drawn handles

App/editor/ViewportPanel.h

@@ -35,7 +35,21 @@ struct GizmoState {
     int op = 7;             // ImGuizmo::TRANSLATE（TRANSLATE_X|Y|Z）
     bool localSpace = true; // 操纵空间：true=模型轴（旋转/缩放语义），
                             // T 键切 world
-    bool dragging = false;  // 拖拽中（IsUsing）→ 鼠标归 Gizmo 不给游戏侧
+    bool dragging = false;  // 拖拽中（IsUsing 或自绘缩放拖拽）→ 鼠标归
+                            // Gizmo 不给游戏侧（Editor::BlockingMouse）
+
+    // ---- 自绘缩放 gizmo（op==SCALE 整体不走 ImGuizmo）----
+    // 库内缩放的 hover/拖拽依赖"法线=轴"平面求交：正对视角（轴⊥
+    // 相机连线）时求交分子恒 0 → 杆抓不到、数值随机猛变；轴∥视线
+    // 时又无屏幕位移。submodule 禁改，AxisMask 只能"藏"不能"补"
+    // → 调用层整体自绘三轴杆 + 中心等比方块（纯屏幕空间数学，任意
+    // 视角良构），实现见 ViewportPanel.cpp ScaleGizmoSelf
+    bool scaleDragActive = false;   // 自绘缩放拖拽中
+    int  scaleDragAxis = -1;        // 拖拽目标：0/1/2 轴；-2 = 中心等比
+    bool scaleHover = false;        // 本帧悬停/拖拽自绘手柄 → 抑制 pick
+    float scaleStartMouse[2] = {0.0f, 0.0f}; // 拖拽起始鼠标（屏幕系）
+    float scaleStartDist = 0.0f;    // 起始鼠标到杆心距离（径向映射用）
+    float scaleStartScale[3] = {1.0f, 1.0f, 1.0f}; // 拖拽起始 scale
 };
 
 class ViewportPanel {