feat(codex-skill): add windows install script

Add a PowerShell installer for the bundled Codex skill so Windows users can install it without relying on bash. Update the English and Chinese README instructions to document the PowerShell command alongside the existing shell installer.

codex-skill/scripts/install.ps1

@@ -0,0 +1,26 @@
+$ErrorActionPreference = "Stop"
+
+$scriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
+$skillDir = Split-Path -Parent $scriptDir
+
+$codexHome = if ($env:CODEX_HOME) {
+    $env:CODEX_HOME
+} elseif ($env:USERPROFILE) {
+    Join-Path $env:USERPROFILE ".codex"
+} else {
+    throw "CODEX_HOME is not set and USERPROFILE is unavailable."
+}
+
+$destRoot = Join-Path $codexHome "skills"
+$destDir = Join-Path $destRoot "cli-anything"
+
+New-Item -ItemType Directory -Path $destRoot -Force | Out-Null
+
+if (Test-Path $destDir) {
+    Write-Error "Refusing to overwrite existing skill: $destDir`nRemove it manually if you want to reinstall."
+}
+
+Copy-Item -Path $skillDir -Destination $destDir -Recurse
+
+Write-Host "Installed Codex skill to: $destDir"
+Write-Host "Restart Codex to pick up the new skill."