feat: Add restore cutout depth extension with edge depth correction

- Introduced a new extension for restoring cutout depth with edge correction.
- Implemented edge depth extension algorithm in `edge_depth.py` to enhance depth accuracy near cutout edges.
- Updated `generate_moge_artifacts` to include an option for extending depth edges during depth generation.
- Modified cutout job processing to enable edge depth extension based on depth request.
- Added comprehensive tests for edge depth functionality, ensuring correct behavior under various scenarios.
- Updated existing node loading functions to remove asset revision dependencies, simplifying the loading process.
- Created new design and proposal documentation outlining the goals and decisions for the extension.

openspec/changes/restore-cutout-depth-extension/proposal.md

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+## Why
+
+Cutout 轮廓附近的背景深度会形成长条拖尾。蜘蛛和恐龙头骨实测表明，生成时延伸深度 4 像素可明显减少拖尾，适合在深度产物生成阶段恢复。
+
+## What Changes
+
+- 仅为 Cutout 深度产物恢复已实测的旧版边缘延伸：可靠来源 Alpha ≥ 0.95、内侧保护 2 px、外侧延伸 4 px、局部平滑。
+- 保留旧算法的来源筛选、分量隔离与回退规则；剪裁 Alpha 继续定义可见轮廓，不新增来源阈值联动或设置。
+- 普通 Depth Plane、全景深度与 Normal 使用原始预测；Cutout 深度及 Metadata 使用同一修复结果。
+
+## Capabilities
+
+### New Capabilities
+
+- `cutout-depth-extension`: Cutout 专用的可靠边缘深度延伸、产物隔离与实图验收。
+
+### Modified Capabilities
+
+无；相关规范尚未归档至 `openspec/specs`。
+
+## Impact
+
+涉及 Cutout Job、共享 MoGe 产物入口、服务端深度处理与相关测试。复用现有 NumPy/SciPy，核对服务端依赖声明。实现范围为生成的 Cutout 深度图及配套 Metadata；几何节点源码、参数、revision 和 `.blend` 资产保持现状。