fix(templates): replace Test-NetConnection with TcpClient in Prepare scripts

Test-NetConnection is Windows-only. Replace with cross-platform TcpClient
async-connect helper (same pattern as Measure-CIBenchmark.ps1) so the
Prepare scripts run on the Linux host under PowerShell.

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

template/Prepare-WinBuild2025.ps1

@@ -163,7 +163,19 @@ param(
 
 Set-StrictMode -Version Latest
 $ErrorActionPreference = 'Stop'
-$ProgressPreference   = 'SilentlyContinue'   # suppress Write-Progress (Test-NetConnection, IWR, etc.)
+$ProgressPreference   = 'SilentlyContinue'   # suppress Write-Progress (IWR, etc.)
+
+function Test-TcpPort {
+    param([string]$ComputerName, [int]$Port, [int]$TimeoutMs = 3000)
+    try {
+        $tcp = [System.Net.Sockets.TcpClient]::new()
+        $ar  = $tcp.BeginConnect($ComputerName, $Port, $null, $null)
+        $ok  = $ar.AsyncWaitHandle.WaitOne($TimeoutMs, $false)
+        $connected = $ok -and $tcp.Connected
+        $tcp.Close()
+        return $connected
+    } catch { return $false }
+}
 
 # ── Locate vmrun.exe ──────────────────────────────────────────────────────────
 $vmrunCandidates = @(
@@ -247,8 +259,7 @@ Write-Host "[Prepare] Waiting for WinRM on $VMIPAddress`:5986 (timeout ${winrmTi
 $winrmDeadline = [datetime]::UtcNow.AddSeconds($winrmTimeoutSec)
 $winrmReady = $false
 while ([datetime]::UtcNow -lt $winrmDeadline) {
-    if (Test-NetConnection -ComputerName $VMIPAddress -Port 5986 `
-            -InformationLevel Quiet -WarningAction SilentlyContinue -ErrorAction SilentlyContinue) {
+    if (Test-TcpPort -ComputerName $VMIPAddress -Port 5986 -TimeoutMs 5000) {
         $winrmReady = $true; break
     }
     Start-Sleep -Seconds 5