refactor(scripts): organize script entry points

scripts/tests/test-install-guards.ps1

@@ -0,0 +1,24 @@
+[CmdletBinding()]
+param([switch]$Summary)
+$ErrorActionPreference = 'Stop'
+$root = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
+. (Join-Path $root 'scripts/lib/manifest.ps1')
+. (Join-Path $root 'scripts/lib/install-targets.ps1')
+
+$work = Join-Path ([System.IO.Path]::GetTempPath()) ("ai-config-install-guard-test-" + [Guid]::NewGuid())
+try {
+    $installed = Join-Path $work 'installed'
+    $missing = Join-Path $work 'missing'
+    New-Item $installed -ItemType Directory -Force | Out-Null
+    New-Item (Get-ManagedManifestPath $installed) -ItemType File -Force | Out-Null
+
+    if (-not (Test-AnyManifestPresent @($installed, $missing))) { throw 'Expected an installed destination to be detected.' }
+    if (Test-AnyManifestPresent @($missing)) { throw 'A destination without a manifest must not count as installed.' }
+    if (Test-AllManifestsPresent @($installed, $missing)) { throw 'Update guard must fail when any selected destination is not installed.' }
+    if (-not (Test-AllManifestsPresent @($installed))) { throw 'Update guard must pass when every selected destination is installed.' }
+
+    if ($Summary) { Write-Output 'Tests: PASS | install guards' } else { Write-Output 'PASS install guards: already-installed and not-installed detection' }
+} finally {
+    Remove-Item $work -Recurse -Force -ErrorAction SilentlyContinue
+}
+exit 0