Add new node asset scripts for geometry and shader operations

- Implemented `build_mesh_plane.py` to create a geometry node group for mesh planes with customizable parameters.
- Created `build_shadeless.py` for a shader node group that displays color without scene lighting while preserving shadows and reflections.
- Added `validate.py` to validate the integrity of the newly created node groups and their inputs.
- Introduced `validate_cutout.py` to ensure the functionality of cutout node groups and their dependencies.
- Developed `validate_mesh_plane.py` to test the mesh plane creation and its modifier settings.

docs/internals/operators/ai-setup.md

@@ -0,0 +1,36 @@
+# AI 环境管理
+
+本页对应 `src/anyimage/operators/ai_setup.py`。该模块把环境安装、必需模型下载和模型缓存清理组织成 Blender 可调用的 Operator。
+
+## 对应文件
+
+```text
+src/anyimage/
+├── operators/ai_setup.py        # 环境与模型管理入口
+├── preferences.py               # 环境位置和扩展级设置
+├── properties.py                # 环境状态与模型目录
+├── runtime.py                   # BlendJob Runtime 访问入口
+└── server/
+    ├── app.py                   # 下载 Job 注册
+    ├── model_catalog.py         # 模型元数据
+    ├── model_download.py        # 模型文件下载
+    └── model_manager.py         # 模型资源与 Session 缓存
+```
+
+## 主流程
+
+```mermaid
+flowchart TD
+    Entry["Set Up AI Environment"] --> Status["读取环境与必需模型状态"]
+    Status --> Ready{"是否全部就绪？"}
+    Ready -- "是" --> Done["结束"]
+    Ready -- "否" --> Environment{"运行环境是否就绪？"}
+    Environment -- "否" --> Install["安装隔离 Python 环境"]
+    Environment -- "是" --> Download["下载缺失的必需模型"]
+    Install --> Download
+    Download --> Done
+```
+
+`SetupAIEnvironment` 是统一入口：首次使用时选择普通源或镜像安装隔离环境；环境已存在时，只补齐必需模型。单模型下载和必需模型批量下载都通过 Job Server 执行，因此状态、错误与进度沿用同一套 Runtime 通道。
+
+`OpenAIEnvironmentSettings` 将用户带到扩展首选项。`ClearModels` 清除 Runtime 中的 `model_manager` 资源，使已加载的模型 Session 释放；它不负责删除磁盘上的模型文件。