fix(artifacts): Retry WinRM connect in Get-BuildArtifacts (wsmprovhost delay)

After Invoke-RemoteBuild closes its session, wsmprovhost.exe may take a moment
to release resources. Subsequent New-PSSession in Get-BuildArtifacts fails with
'WSMan service could not launch a host process'.

Add retry loop: 3 attempts, 10s backoff. Enough for WinRM to recover between
the build session and artifact collection session.

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

scripts/Get-BuildArtifacts.ps1

@@ -68,14 +68,26 @@ if (-not (Test-Path $HostArtifactDir)) {
 $sessionOptions = New-CISessionOption
 
 Write-Host "[Get-BuildArtifacts] Connecting to VM at $IPAddress..."
-$session = New-PSSession `
-    -ComputerName   $IPAddress `
-    -Credential     $Credential `
-    -SessionOption  $sessionOptions `
-    -UseSSL `
-    -Port           5986 `
-    -Authentication Basic `
-    -ErrorAction    Stop
+$session  = $null
+$attempts = 3
+$delay    = 10   # seconds between attempts
+for ($i = 1; $i -le $attempts; $i++) {
+    try {
+        $session = New-PSSession `
+            -ComputerName   $IPAddress `
+            -Credential     $Credential `
+            -SessionOption  $sessionOptions `
+            -UseSSL `
+            -Port           5986 `
+            -Authentication Basic `
+            -ErrorAction    Stop
+        break
+    } catch {
+        if ($i -eq $attempts) { throw }
+        Write-Warning "[Get-BuildArtifacts] WinRM connect attempt $i/$attempts failed — retrying in ${delay}s... ($_)"
+        Start-Sleep -Seconds $delay
+    }
+}
 
 try {
     # ── Verify artifact exists in guest ──────────────────────────────────