Add tests for image layer, image plane, inventory, saved layout, commands, documentation, manifest, and packaging

- Implement tests for image layer functionality including alpha curve and depth layer behavior.
- Create tests for image plane evaluation and modifier input handling.
- Add tests to verify the saved asset inventory and its persistence.
- Introduce tests for the documentation command to ensure correct project version deployment.
- Validate the extension manifest structure and required permissions.
- Develop tests for the packaging process, ensuring correct platform handling and dependency management.
- Enhance image depth plane group functionality with new split threshold input and surface processing.

docs/internals/development.md

@@ -27,7 +27,7 @@ Blender Stub 共用 `blender_test_support.py`；Server 和实际 Blender 几何
 | --- | --- |
 | `uv run pack` | 生成 Windows、macOS arm64、Linux 扩展包 |
 | `uv run pack --prepare` | 为本机同步扩展 wheel 与 Manifest |
-| `uv run build_node` | 构建、验证节点资产并运行测试 |
+| `uv run build_nodes` | 构建、验证节点资产并运行测试 |
 | `uv run sync_models` | 准备、校验并上传模型声明的文件 |
 | `uv run docs -dev` | 本地预览文档 |
 | `uv run docs` | 通过 Mike 发布项目版本并更新 latest |