feat(install-options): add npm CLI reinstall helpers (PowerShell)

Test-GlobalNpmPackage, Get-CliNpmPackage, Read-CliReinstallOption, and
Invoke-CliReinstall let install.ps1 offer uninstalling and reinstalling
a client CLI through npm. Not wired into install.ps1 yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/lib/install-options.ps1

@@ -46,6 +46,61 @@ function Test-GlobalNpmCodex {
     }
 }
 
+function Test-GlobalNpmPackage {
+    param([Parameter(Mandatory=$true)][string]$Package)
+    $npm = Get-Command npm -ErrorAction SilentlyContinue
+    if (-not $npm) { return $false }
+    $previousPreference = $ErrorActionPreference
+    try {
+        $ErrorActionPreference = 'Continue'
+        & $npm list -g $Package --depth=0 --json 1>$null 2>$null
+        return $LASTEXITCODE -eq 0
+    } finally {
+        $ErrorActionPreference = $previousPreference
+    }
+}
+
+function Get-CliNpmPackage {
+    param([ValidateSet('codex','claude')][Parameter(Mandatory=$true)][string]$Client)
+    if ($Client -eq 'codex') { return '@openai/codex' }
+    return '@anthropic-ai/claude-code'
+}
+
+function Read-CliReinstallOption {
+    <#
+    .SYNOPSIS
+        Asked once per install run, never persisted; a dry run never prompts and never previews it.
+    #>
+    param([string]$Client, [switch]$DryRun)
+    if ($DryRun) { return $false }
+    return Read-InstallBoolean -Prompt "Uninstall $Client and reinstall via npm?" -Default $false
+}
+
+function Invoke-CliReinstall {
+    param([string]$Client, [switch]$DryRun, [switch]$Summary)
+    $clients = if ($Client -eq 'Both') { @('codex', 'claude') } else { @($Client.ToLowerInvariant()) }
+    $previousAutoUpdate = $env:CLAUDE_CODE_PACKAGE_MANAGER_AUTO_UPDATE
+    try {
+        $env:CLAUDE_CODE_PACKAGE_MANAGER_AUTO_UPDATE = '1'
+        foreach ($selectedClient in $clients) {
+            if ($selectedClient -eq 'codex' -and -not $DryRun -and (Test-CodexProcessActive)) {
+                Write-Warning 'Codex CLI reinstall skipped because codex.exe is running. Close all Codex sessions and run install again to reinstall the CLI.'
+                continue
+            }
+            $package = Get-CliNpmPackage -Client $selectedClient
+            if (Test-GlobalNpmPackage -Package $package) {
+                Invoke-PluginCommand -Command 'npm' -Arguments @('uninstall', '-g', $package) -DryRun:$DryRun -Summary:$Summary
+            } else {
+                Write-Warning "$selectedClient CLI was not found as a global npm package; a non-npm installation cannot be removed automatically. Installing $package via npm alongside it."
+            }
+            Invoke-PluginCommand -Command 'npm' -Arguments @('install', '-g', "$package@latest") -DryRun:$DryRun -Summary:$Summary
+            if ($Summary) { Write-Output "CLI $selectedClient reinstall: $(if ($DryRun) { 'dry-run' } else { 'PASS' })" }
+        }
+    } finally {
+        $env:CLAUDE_CODE_PACKAGE_MANAGER_AUTO_UPDATE = $previousAutoUpdate
+    }
+}
+
 function Update-SelectedAgentClis {
     param([string]$Client, [switch]$DryRun, [switch]$Summary)
     $clients = if ($Client -eq 'Both') { @('codex', 'claude') } else { @($Client.ToLowerInvariant()) }