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/code.mdx

@@ -0,0 +1,35 @@
+---
+title: "Code blocks"
+description: "Display inline code and code blocks"
+icon: "code"
+---
+
+## Inline code
+
+To denote a `word` or `phrase` as code, enclose it in backticks (`).
+
+```
+To denote a `word` or `phrase` as code, enclose it in backticks (`).
+```
+
+## Code blocks
+
+Use [fenced code blocks](https://www.markdownguide.org/extended-syntax/#fenced-code-blocks) by enclosing code in three backticks and follow the leading ticks with the programming language of your snippet to get syntax highlighting. Optionally, you can also write the name of your code after the programming language.
+
+```java HelloWorld.java
+class HelloWorld {
+    public static void main(String[] args) {
+        System.out.println("Hello, World!");
+    }
+}
+```
+
+````md
+```java HelloWorld.java
+class HelloWorld {
+    public static void main(String[] args) {
+        System.out.println("Hello, World!");
+    }
+}
+```
+````