fix(scripts): satisfy PSScriptAnalyzer (lint gate)

- Remove-Securely: suppress PSUseShouldProcessForStateChangingFunctions
  (internal best-effort shred; ShouldProcess prompts are undesirable)
  + add [CmdletBinding()].
- Replace the two empty catch blocks (Set-CIGuestCredential.ps1,
  Test-CIGuestWinRM.ps1) with Write-Verbose so PSAvoidUsingEmptyCatchBlock
  is satisfied while keeping best-effort behavior.

scripts/Test-CIGuestWinRM.ps1

@@ -116,7 +116,9 @@ try {
     $cn = $ssl.RemoteCertificate.Subject  # e.g. "CN=WINBUILD"
     if ($cn -match 'CN=([^,]+)') { $guestCn = $Matches[1].Trim() }
     $ssl.Dispose(); $tcpc.Close()
-} catch { }
+} catch {
+    Write-Verbose "cert CN probe failed (hostname auto-detect skipped): $_"
+}
 if ($guestCn) {
     Write-Host "      guest cert CN (hostname): $guestCn" -ForegroundColor Cyan
 }