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>

template/Prepare-WinBuild2025.ps1

@@ -8,8 +8,9 @@
       1. Pre-flight validation: script presence, IP octet range, TCP/5986 reachable
       2. Configures host WinRM client (TrustedHosts only, HTTPS needs no AllowUnencrypted) — restored on exit
       3. Validates host WinRM TrustedHosts applied correctly
-      4. Tests WinRM HTTPS connectivity (Test-WSMan -UseSSL -Port 5986) — fails fast with actionable message
-      5. Opens PSSession to the VM
+      4. Opens PSSession -UseSSL -Port 5986 -SkipCACheck — fails fast with actionable message
+         (PS 5.1 Test-WSMan has no -SessionOption, so PSSession is used as the connectivity probe)
+      5. PSSession open — step 4 and 5 are now merged
       6. Ensures C:\CI exists on guest; validates creation
       7. Copies Setup-WinBuild2025.ps1 into the VM; validates file present + size match
       8. Runs Setup-WinBuild2025.ps1 inside the VM with the given parameters
@@ -260,7 +261,6 @@ else {
 }
 
 $sessionOptions = New-PSSessionOption -SkipCACheck -SkipCNCheck -SkipRevocationCheck
-$wsmOpt         = New-WSManSessionOption -SkipCACheck -SkipCNCheck -SkipRevocationCheck
 
 # ── Configure HOST-side WinRM client (TrustedHosts for HTTPS Basic auth) ──────
 # HTTPS/5986 does not require AllowUnencrypted on the host side. Only TrustedHosts
@@ -288,16 +288,21 @@ catch {
 }
 
 
-Write-Host "[Prepare] Testing WinRM HTTPS connectivity to $VMIPAddress`:5986..."
-try {
-    Test-WSMan -ComputerName $VMIPAddress -Port 5986 -UseSSL `
-        -SessionOption $wsmOpt -Credential $credential `
-        -Authentication Basic -ErrorAction Stop | Out-Null
-    Write-Host "[Prepare] WinRM HTTPS reachable."
-}
-catch {
+# ── Open session (Test-WSMan skipped — PS 5.1 Test-WSMan has no -SessionOption for HTTPS) ──
+# New-PSSession with -SkipCACheck handles cert validation for self-signed lab cert.
+Write-Host "[Prepare] Opening PSSession to $VMIPAddress`:5986 (HTTPS)..."
+$session = try {
+    New-PSSession `
+        -ComputerName   $VMIPAddress `
+        -Credential     $credential `
+        -SessionOption  $sessionOptions `
+        -UseSSL `
+        -Port           5986 `
+        -Authentication Basic `
+        -ErrorAction    Stop
+} catch {
     Write-Error @"
-[Prepare] Cannot reach $VMIPAddress via WinRM HTTPS (port 5986).
+[Prepare] Cannot open PSSession to $VMIPAddress via WinRM HTTPS (port 5986).
 
 Ensure:
   - The VM is running and on VMnet8 (NAT) with internet access
@@ -311,17 +316,6 @@ Error: $_
     exit 1
 }
 
-# ── Open session ──────────────────────────────────────────────────────────────
-Write-Host "[Prepare] Opening PSSession..."
-$session = New-PSSession `
-    -ComputerName   $VMIPAddress `
-    -Credential     $credential `
-    -SessionOption  $sessionOptions `
-    -UseSSL `
-    -Port           5986 `
-    -Authentication Basic `
-    -ErrorAction    Stop
-
 try {
     # ── Copy Setup-WinBuild2025.ps1 into the VM ───────────────────────────────
     $setupScript     = Join-Path $scriptDir 'Setup-WinBuild2025.ps1'
@@ -415,11 +409,12 @@ try {
         while ((Get-Date) -lt $deadline) {
             Start-Sleep -Seconds 10
             try {
-                $wsm = New-WSManSessionOption -SkipCACheck -SkipCNCheck -SkipRevocationCheck
-                $r = Test-WSMan -ComputerName $IP -Port 5986 -UseSSL `
-                     -SessionOption $wsm -Credential $Cred `
-                     -Authentication Basic -ErrorAction Stop
-                if ($r) { return $true }
+                # Test-WSMan has no -SessionOption in PS 5.1 — use New-PSSession as probe.
+                $probe = New-PSSession -ComputerName $IP -Port 5986 -UseSSL `
+                             -SessionOption $SessionOptions -Credential $Cred `
+                             -Authentication Basic -ErrorAction Stop
+                Remove-PSSession $probe -ErrorAction SilentlyContinue
+                return $true
             } catch { }
         }
         return $false