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- Removed outdated logic and ensured all changes are documented and tested for regression.

openspec/changes/refine-image-output-semantics/specs/image-result-materials/spec.md

@@ -0,0 +1,16 @@
+## ADDED Requirements
+
+### Requirement: Image color drives generated material IOR Level
+系统 SHALL 将 Plane、Depth Plane 与 Cutout 的非 Shadeless 生成材质中 `O Image Layer` 的 Color 输出直接连接到 Principled BSDF 的 IOR Level，同时保留既有 IOR、Base Color、Roughness、Alpha、Normal 与 Displacement 连接。
+
+#### Scenario: Dark image content suppresses highlights
+- **WHEN** 生成材质采样到黑色或暗色图片内容
+- **THEN** Principled BSDF 的 IOR Level SHALL 接收对应的低颜色值，从而降低该区域的高亮
+
+#### Scenario: Bright image content preserves direct color response
+- **WHEN** 生成材质采样到白色或亮色图片内容
+- **THEN** Principled BSDF 的 IOR Level SHALL 接收 `O Image Layer` Color 的直接转换值，不经过额外缩放或固定上限
+
+#### Scenario: Generated material keeps its IOR value
+- **WHEN** Cutout 或 Depth Plane 以 IOR `1.2` 创建材质
+- **THEN** 系统 SHALL 保留 IOR `1.2`，并由 Color 独立驱动 IOR Level