fix(install.ps1): camoufox-cli 用 .cmd shim 替代 npm install -g + plugins list stderr

[bigbrother666sh]

两个 Win 实测卡点（v5.6.0，Administrator 用户）：

1. camoufox-cli 全局装 EEXIST

npm error code EEXIST
npm error path C:\Users\Administrator\xiaobei\camoufox-cli
npm error EEXIST: file already exists

根因：npm install -g $fork 在 Windows 上把 fork 装进 $prefix\node_modules 时撞 fork 源目录本身。Windows npm 不能像 Linux/mac 那样 symlink 到源目录（EEXIST on the fork dir）。

修法：仿 openclaw.cmd 写 $Root\bin\camoufox-cli.cmd shim 直接跑 node $fork\dist\cli.js（fork 的 node_modules 已就位，Node 从 cli.js 向上解析依赖；camoufox-cli JS 用 __dirname 定位包根，行为与全局装一致）。前置 $Root\bin 进 PATH 让后续 camoufox-cli install 找得到 shim。去掉 npm_config_prefix 和 npm install -g。

2. plugins list stderr NativeCommandError

openclaw.cmd : [state-migrations] Legacy state migration warnings:
+ $listOut = (& $ClawCmd plugins list 2>$null | Out-String)
+ FullyQualifiedErrorId : NativeCommandError

根因：2>$null 在 Windows PowerShell 5.1 + Stop 下压不住 .cmd 的 stderr，仍抛 NativeCommandError（[[34-win-install-ps1-stderr-stop-gotcha]] 同类坑）。

修法：加 Capture-Streamed helper（临时 Continue + 2>&1 + Out-String）替换。

验证

install.ps1 走 raw URL 拉取（irm raw.githubusercontent.com/.../master/scripts/install.ps1 | iex），合 master 即生效，无需重建 tarball。Auto Release 已禁用，合此 PR 不 bump 版本，保持 v5.6.0。

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