Refactor depth node groups and simplify options

- Removed `Smooth Weight` input from `O Image Depth Plane`, `O Image Depth Cutout`, and `O Image Depth Panorama` to streamline the interface and maintain consistent boundary smoothing behavior.
- Adjusted the `Reference Depth` input to appear last in the options panel for better organization, reflecting its role as a calibration value.
- Consolidated the `expand_smooth()` function to only accept necessary parameters, eliminating unused branches related to `Smooth Weight` and `pin_sharp`.
- Updated related tests and node assets to ensure functionality remains intact and consistent with the new structure.
- Introduced new specifications to document the changes and ensure compliance with the updated requirements.

openspec/changes/simplify-depth-group-options/tasks.md

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+## 1. 共享平滑收敛
+
+- [x] 1.1 将 `expand_smooth()` 收敛为影响场形态，删除 `weight_name`、`pin_sharp` 与无影响场分支
+- [x] 1.2 更新 `smooth_cut_boundary()` 调用并确认影响带、保护规则与轮廓权重不变
+
+## 2. 节点组接口
+
+- [x] 2.1 从 Depth Plane、Depth Cutout、Depth Panorama 删除 `Smooth Weight` 输入
+- [x] 2.2 将 Depth Plane、Depth Cutout、Relief Plane 的 `Reference Depth` 移到 Options 最后一项
+
+## 3. 测试与资产
+
+- [x] 3.1 更新节点库存、Options 排列与边界平滑行为测试，移除 `Smooth Weight` 依赖
+- [x] 3.2 运行 `uv run node-group build` 重建并验证节点资产
+- [x] 3.3 运行节点与 Operator 相关测试，检查残留引用与最终差异