docs: add junction-safe unlink rule to defensive patterns

docs/defensive-patterns.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/defensive-patterns.md
-defensive-patterns.md: b6e643cad6180ea35a363f2c4131b2c24f5f70af
-defensive-patterns.zh.md: e1a6abdfd2138a51a13ceaf418bf6df1d0c65579
+defensive-patterns.md: 9db582354628a13abd43c5bd052dbbfd6e52f79f
+defensive-patterns.zh.md: 7bebbe3c1964f2b826afc523eaa4af7be180e36e

docs/defensive-patterns.md

@@ -27,3 +27,7 @@ A user-supplied listener that throws must not reject the promise it runs inside
 ## Never hand untrusted output the ambient environment or predictable paths
 
 Spawned commands get a scrubbed env (drop `*KEY*`/`*SECRET*`/`*TOKEN*`/`*PASSWORD*`) so harness credentials cannot leak into output, `env`, or spill files. Temp/spill files use a private (0700) dir, random names, and exclusive owner-only opens (`'wx'`, `0o600`) — predictable world-readable paths invite symlink races and disclosure.
+
+## Unlink link-shaped paths
+
+A path that may be a symlink or Windows junction is removed with `lstatSync().isSymbolicLink()` then `unlinkSync`: unlink deletes only the link and refuses a real directory, so it never follows the link into its target. Windows `rmSync(link)` throws `ERR_FS_EISDIR` on a junction; recursive deletion may descend through one into its target. Reserve recursive `rmSync` for known real directories.

docs/defensive-patterns.zh.md

@@ -26,4 +26,8 @@
 
 ## 绝不将环境变量或可预测路径暴露给不可信输出
 
-启动的命令应使用经过清理的环境变量，移除名称匹配 `*KEY*`、`*SECRET*`、`*TOKEN*` 或 `*PASSWORD*` 的项，防止 harness 凭证通过命令输出、`env` 或 spill 文件泄漏。临时文件和 spill 文件应放在权限为 0700 的私有目录中，使用随机文件名，并以独占且仅所有者可访问的方式打开（`'wx'`、`0o600`）；可预测且所有用户均可读的路径会引发符号链接竞态和信息泄露。
+启动的命令应使用经过清理的环境变量，移除名称匹配 `*KEY*`、`*SECRET*`、`*TOKEN*` 或 `*PASSWORD*` 的项，防止 harness 凭证通过命令输出、`env` 或 spill 文件泄漏。临时文件和 spill 文件应放在权限为 0700 的私有目录中，使用随机文件名，并以独占且仅所有者可访问的方式打开（`'wx'`、`0o600`）；可预测且全局可读的路径会引发符号链接竞态和信息泄露。
+
+## 用 unlink 删除链接形态的路径
+
+可能是符号链接或 Windows junction 的路径，应先用 `lstatSync().isSymbolicLink()` 判断，再用 `unlinkSync` 删除：unlink 只删除链接本身并拒绝真实目录，因此绝不会跟随链接进入其目标。Windows 上对 junction 调用 `rmSync(link)` 会抛 `ERR_FS_EISDIR`；递归删除可能穿过 junction 进入其目标。真实目录才使用带 `recursive` 的 `rmSync`。