feat(docs): Markdown 展示路由中间件 (issue #4)

[yourtion]

关联 issue

Closes #4

改动内容

middlewares 此前已通过 .middlewares() 注册并经 DOC_FIELD 采集进文档数据，但四个生成器无一渲染。

• Markdown 在「请求地址」行下方输出 中间件：<fn1>, <fn2>（取具名函数 fn.name，匿名函数跳过）
• Swagger/Postman 不改动：OpenAPI 标准无 middleware 字段，强行加入不被消费方识别

测试

• 新增 3 个回归测试（具名中间件 / 无中间件 / 匿名跳过）
• 全量 npm run test:lib：317 → 320 全绿
• tsc --noEmit 通过

版本

bump 3.2.1 → 3.2.5，已登记 MIGRATION

合并顺序提示

本系列共 4 个 PR，请按版本号顺序合并（3.2.2 → 3.2.3 → 3.2.4 → 3.2.5）。
⚠️ 合并时 MIGRATION.md 与 package.json 可能冲突，需 rebase 解冲突。

相关

issue #3（API 版本）已 wontfix 关闭：与「热路径零分配」「hook 不参与控制流」架构红线冲突，已有 groups[].prefix 替代方案。

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.57%. Comparing base (ffe0ffa) to head (62fd775).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #197      +/-   ##
==========================================
+ Coverage   92.54%   92.57%   +0.02%     
==========================================
  Files          28       28              
  Lines        2939     2948       +9     
  Branches      770      773       +3     
==========================================
+ Hits         2720     2729       +9     
  Misses        217      217              
  Partials        2        2              

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