feat: workflow designer agent and Generate dialog

docs/user_guide/en/web_ui_guide.md

@@ -20,6 +20,9 @@ View and manage all available workflow YAML files.
 - Browse workflows in `yaml_instance/` directory
 - Preview YAML configuration content
 - Select workflow to execute or edit
+- **Generate**: describe a workflow in plain language and an agent writes the YAML (see below)
+
+**Generating a workflow**: Generate runs `yaml_instance/workflow_designer.yaml` with the server's `BASE_URL`, `API_KEY` and its `MODEL_NAME` (default `gpt-4o`). The designer reads the authoring guide, node docs and bundled examples through function tools, then validates its YAML with the same check the save route uses. Its validator also requires every agent node to use the `${BASE_URL}`, `${API_KEY}` and `${MODEL_NAME}` placeholders and rejects anything that looks like an API key. The result opens in an editable preview; **Save and open** writes it to `yaml_instance/<name>.yaml` and opens it in the workbench. If the YAML still fails validation, the errors are listed as comments at the top; schema errors also block saving. The same workflow runs headless: `echo "your description" | uv run python run.py --path yaml_instance/workflow_designer.yaml --name designer`.
 
 ### 2.3 Launch View
 

docs/user_guide/zh/web_ui_guide.md

@@ -20,6 +20,9 @@
 - 浏览 `yaml_instance/` 目录下的工作流
 - 预览 YAML 配置内容
 - 选择工作流进入执行或编辑
+- **生成 (Generate)**：用自然语言描述工作流，由智能体编写 YAML（见下文）
+
+**生成工作流**：“生成”会使用服务器的 `BASE_URL`、`API_KEY` 以及工作流自身的 `MODEL_NAME`（默认 `gpt-4o`）运行 `yaml_instance/workflow_designer.yaml`。设计器通过函数工具阅读编写指南、节点文档和内置示例，并用与保存接口相同的校验检查生成的 YAML。它的校验还要求每个智能体节点使用 `${BASE_URL}`、`${API_KEY}` 和 `${MODEL_NAME}` 占位符，并拒绝任何疑似 API 密钥的内容。结果显示在可编辑的预览中；**保存并打开**会将其写入 `yaml_instance/<名称>.yaml` 并在工作台中打开。若 YAML 仍未通过校验，错误会以注释形式列在顶部；结构错误同样会阻止保存。也可以在命令行运行：`echo "你的描述" | uv run python run.py --path yaml_instance/workflow_designer.yaml --name designer`。
 
 ### 2.3 启动页 (Launch View)