docs(i18n): cookbook batch — six bilingual pairs via the committed pipeline

六篇 cookbook 全部配对（adding-a-package / adding-a-tool /
adding-a-vendored-package / adding-an-llm-adapter /
extension-cookbook / responding-to-pr-review-on-a-stack）：译文由
进仓流水线产出（translation-prompt.md 全占位符渲染 + 5 组金标
few-shot），双侧语言切换行齐备，六篇加入 manifest required（15）。
另补 prompt 的 When translating into English 一节（此前为占位）：
标点/术语双向绑定/主语显化/惯用语概念还原/语域，与
translation-rules 的中文先行条款一致。

docs/cookbook/adding-a-vendored-package.md

@@ -1,5 +1,7 @@
 # Cookbook: adding a vendored package
 
+English | [中文](adding-a-vendored-package.zh.md)
+
 When the harness needs another upstream Cordis package (e.g. `@cordisjs/plugin-http`), it is **vendored** as pinned source under `vendor/`, not added as an npm dependency — see [the vendoring decision](../rfc/implemented/process/2026-06-11-vendor-cordis-as-source.md) for why. [vendor/README.md](../../vendor/README.md) covers *updating* an already-vendored package; this guide is the file-by-file checklist for adding a **new** one. (Verified against the existing vendored set; if it drifts, fix it here.)
 
 ## 1. Copy the source in