Refactor Cutout and Image Editing Logic

- Renamed "Base Plane Depth" to "Reference Depth" across validate_cutout.py for consistency.
- Introduced a new specification for Cutout mesh sampling to ensure source pixel spacing is preserved and limits are applied correctly.
- Unified naming conventions for image editing results to maintain consistency across Remove Background, Upscale, and Crop operations.
- Updated the handling of Refine Selection to ensure it retains the original bounds and does not apply unnecessary cropping.
- Enhanced material generation logic to connect image color directly to IOR Level, improving the rendering of dark areas.
- Established clear requirements for geometry depth controls and image result materials to ensure consistent behavior across different components.
- Removed outdated logic and ensured all changes are documented and tested for regression.

docs/internals/operators/convert-to-plane.md

@@ -39,13 +39,13 @@ EXR 的 RGB 重复保存完整相机 Z，Alpha 保存模型 Validity；JSON 保
 
 ### 创建 Depth Plane
 
-Job 返回后，`object.create_depth_plane_from_result()` 加载并 Pack `z-depth.exr` 与 `tangent-normal.png`。Depth 数据块仍由 `depth_data_name()` 命名；Normal 图片设为 Non-Color，并以 Tangent Space 接入 `O Image Layer`。结果材质与 Cutout 一样使用 Principled IOR `1.2`。`depth.json` 的参考深度乘以统一尺度后初始化 **Base Plane Depth**，使它和采样深度处于同一局部距离单位。
+Job 返回后，`object.create_depth_plane_from_result()` 加载并 Pack `z-depth.exr` 与 `tangent-normal.png`。Depth 数据块仍由 `depth_data_name()` 命名；Normal 图片设为 Non-Color，并以 Tangent Space 接入 `O Image Layer`。结果材质与 Cutout 一样使用 Principled IOR `1.2`，并由 `O Image Layer` Color 直接驱动 IOR Level。`depth.json` 的参考深度乘以统一尺度后初始化 **Reference Depth**，使它和采样深度处于同一局部距离单位。
 
 `O Image Depth Plane` 把 `O Mesh Plane` 的固定底面放在原图片平面，`Thickness` 只沿正法线移动可变面与中间环，再按各层位置应用深度位移：
 
 ```mermaid
 flowchart TD
-    Depth["Z Depth × Uniform Scale"] --> Offset["(Base Plane Depth - Depth) × Depth Scale"]
+    Depth["Z Depth × Uniform Scale"] --> Offset["(Reference Depth - Depth) × Depth Scale"]
     Offset --> Clamp["负向位移限制在固定底面之前"]
     Block["O Mesh Plane 厚度体块"] --> Weight["固定底面 0 → 中间环 → 可变面 1"]
     Clamp --> Apply["位移 × 层权重"]