feat: 品牌替换 + 启动优化 + AGENTS.md 模板定制

- 品牌替换：OpenCode/opencode → AirCoding/aircoding（16+ 文件）
- Logo ASCII art：修复 left/right 行数不匹配导致的启动崩溃
- 启动诊断：添加 OPENCODE_PRINT_TIMING 计时探针
- dev 模式默认 --pure 跳过外部插件加载
- AGENTS.md 模板：追加 AirCoding 多 Agent 专项段落
- architect prompt + plugin：强化 AGENTS.md 产出验证

packages/docs/essentials/reusable-snippets.mdx

@@ -0,0 +1,112 @@
+---
+title: "Reusable snippets"
+description: "Reusable, custom snippets to keep content in sync"
+icon: "recycle"
+---
+
+import SnippetIntro from "/snippets/snippet-intro.mdx"
+
+<SnippetIntro />
+
+## Creating a custom snippet
+
+**Pre-condition**: You must create your snippet file in the `snippets` directory.
+
+<Note>
+  Any page in the `snippets` directory will be treated as a snippet and will not be rendered into a standalone page. If
+  you want to create a standalone page from the snippet, import the snippet into another file and call it as a
+  component.
+</Note>
+
+### Default export
+
+1. Add content to your snippet file that you want to re-use across multiple
+   locations. Optionally, you can add variables that can be filled in via props
+   when you import the snippet.
+
+```mdx snippets/my-snippet.mdx
+Hello world! This is my content I want to reuse across pages. My keyword of the
+day is {word}.
+```
+
+<Warning>
+  The content that you want to reuse must be inside the `snippets` directory in order for the import to work.
+</Warning>
+
+2. Import the snippet into your destination file.
+
+```mdx destination-file.mdx
+---
+title: My title
+description: My Description
+---
+
+import MySnippet from "/snippets/path/to/my-snippet.mdx"
+
+## Header
+
+Lorem impsum dolor sit amet.
+
+<MySnippet word="bananas" />
+```
+
+### Reusable variables
+
+1. Export a variable from your snippet file:
+
+```mdx snippets/path/to/custom-variables.mdx
+export const myName = "my name"
+
+export const myObject = { fruit: "strawberries" }
+
+;
+```
+
+2. Import the snippet from your destination file and use the variable:
+
+```mdx destination-file.mdx
+---
+title: My title
+description: My Description
+---
+
+import { myName, myObject } from "/snippets/path/to/custom-variables.mdx"
+
+Hello, my name is {myName} and I like {myObject.fruit}.
+```
+
+### Reusable components
+
+1. Inside your snippet file, create a component that takes in props by exporting
+   your component in the form of an arrow function.
+
+```mdx snippets/custom-component.mdx
+export const MyComponent = ({ title }) => (
+  <div>
+    <h1>{title}</h1>
+    <p>... snippet content ...</p>
+  </div>
+)
+
+;
+```
+
+<Warning>
+  MDX does not compile inside the body of an arrow function. Stick to HTML syntax when you can or use a default export
+  if you need to use MDX.
+</Warning>
+
+2. Import the snippet into your destination file and pass in the props
+
+```mdx destination-file.mdx
+---
+title: My title
+description: My Description
+---
+
+import { MyComponent } from "/snippets/custom-component.mdx"
+
+Lorem ipsum dolor sit amet.
+
+<MyComponent title={"Custom title"} />
+```