fix(winrm-https): PS 5.1 Test-WSMan has no -SessionOption — remove from all call sites

Test-WSMan in Windows PowerShell 5.1 does not support -SessionOption (WSManSessionOption),
causing "Cannot find a parameter matching the name 'SessionOption'" at runtime.

Prepare-WinBuild2025.ps1:
  - Remove Test-WSMan connectivity check step entirely
  - Open New-PSSession directly (handles -SkipCACheck via PSSessionOption)
  - Wrap New-PSSession in try/catch with the same actionable error message
  - Remove $wsmOpt (WSManSessionOption) — no longer needed
  Wait-GuestWinRMReady: replace Test-WSMan probe with New-PSSession probe + Remove-PSSession

Wait-VMReady.ps1:
  - Remove $wsmOpt entirely
  - Replace Test-WSMan -UseSSL -SessionOption with Test-NetConnection -Port 5986
    (TCP open on 5986 = HTTPS listener up = VM ready; credentials not available here)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/Wait-VMReady.ps1

@@ -68,7 +68,6 @@ $deadline    = (Get-Date).AddSeconds($TimeoutSeconds)
 $attempt     = 0
 $phase       = 'vmrun-state'   # tracks current phase for informative output
 $lastPhase   = ''
-$wsmOpt      = New-WSManSessionOption -SkipCACheck -SkipCNCheck -SkipRevocationCheck
 
 Write-Host "[Wait-VMReady] Waiting for VM ready (timeout: ${TimeoutSeconds}s, IP: $IPAddress)..."
 
@@ -108,14 +107,17 @@ while ((Get-Date) -lt $deadline) {
         }
     }
 
-    # ── Phase 3: WinRM responsive ────────────────────────────────────────
-    try {
-        Test-WSMan -ComputerName $IPAddress -Port 5986 -UseSSL -SessionOption $wsmOpt -ErrorAction Stop | Out-Null
-        # Success — VM is ready
+    # ── Phase 3: WinRM port 5986 accepting TCP connections ───────────────
+    # Test-WSMan has no -SessionOption in PS 5.1 and fails cert validation for
+    # self-signed certs. TCP open on 5986 = HTTPS listener up = VM ready.
+    $winrmUp = Test-NetConnection -ComputerName $IPAddress -Port 5986 `
+                   -InformationLevel Quiet -WarningAction SilentlyContinue `
+                   -ErrorAction SilentlyContinue
+    if ($winrmUp) {
         Write-Host "[Wait-VMReady] VM ready after ~$([int]($attempt * $PollIntervalSeconds))s (attempt $attempt)."
         return
     }
-    catch {
+    else {
         $phase = 'winrm'
         if ($lastPhase -ne $phase) {
             Write-Host "[Wait-VMReady] Phase 3/3: ping OK, waiting for WinRM on port 5986 (HTTPS)..."