fix: Export-RdpRepairDiagnosticReport ломался на одном cert (foreach PS 5.1)

foreach по PSCustomObject перечисляет свойства, не cert — нужен @().
Рекурсивное flatten в Get-RdpRepairCertificateArray, самотест Export-паттерна.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/Invoke-RdpRepairSelfTest.ps1

@@ -100,6 +100,22 @@ Assert-Test 'Get-RdpRepairCertificateArray flattens nested Object[]' {
     if ($first.Thumbprint -ne 'NESTED01') { throw "expected NESTED01 got $($first.Thumbprint)" }
 }
 
+Assert-Test 'foreach must use @() wrapper on single cert (Export pattern)' {
+    $mock = [PSCustomObject]@{
+        Thumbprint = 'LOOP01'
+        Subject    = 'CN=loop'
+        NotAfter   = (Get-Date).AddDays(1)
+        HasKey     = $true
+    }
+    $lines = @()
+    foreach ($c in @(Get-RdpRepairCertificateArray @($mock))) {
+        $lines += $c.Subject
+    }
+    if ($lines.Count -ne 1 -or $lines[0] -ne 'CN=loop') {
+        throw "expected CN=loop got $($lines -join ',')"
+    }
+}
+
 Assert-Test 'Get-RdpRepairDiagnosticSnapshot object shape' {
     if (-not (Test-RdpRepairIsAdministrator)) {
         Write-Host '  (skip snapshot fields - not admin)' -ForegroundColor DarkYellow