Fix deploy wipe/extract race that could break admin site deploys

Remove-Item can report success while NTFS is still asynchronously
finishing a large recursive delete, so Expand-Archive -Force could
see leftover entries, queue them for removal itself, and lose the
race against our own delete completing - failing with "Cannot find
path ... because it does not exist" on the next deploy.

scripts/deploy-iis-remote-apply.ps1

@@ -53,23 +53,38 @@ function Wait-AppPoolFullyStopped {
 # Wipes are attempted a few times with a short pause - file handles (IIS or AV scanning
 # the just-stopped worker process's files) can take a moment to release even after the
 # worker process itself is confirmed gone.
+#
+# Remove-Item returning without an error is not proof the directory is actually empty yet -
+# NTFS can finish a large recursive delete asynchronously, so a Get-ChildItem right after can
+# still show remnants. If Expand-Archive -Force then runs against those remnants, it queues
+# them for removal itself and can lose the race against our own delete finishing, failing with
+# "Cannot find path ... because it does not exist". So after Remove-Item reports success, poll
+# until the directory is verifiably empty before trusting the wipe is done.
 function Remove-DirectoryContentsWithRetry {
-  param([string]$Path, [int]$MaxAttempts = 5, [int]$DelayMs = 2000)
+  param([string]$DirPath, [int]$MaxAttempts = 5, [int]$DelayMs = 2000)
 
   for($attempt = 1; $attempt -le $MaxAttempts; $attempt++){
-    $failure = $null
+    $problem = $null
     try {
-      Remove-Item -Recurse -Force $Path -ErrorAction Stop
-      return
+      Remove-Item -Recurse -Force (Join-Path $DirPath '*') -ErrorAction Stop
     } catch {
-      $failure = $_
-      if($attempt -lt $MaxAttempts){
-        Write-Host "Wipe attempt $attempt failed (files still locked?) - retrying in $($DelayMs)ms"
-        Start-Sleep -Milliseconds $DelayMs
+      $problem = "delete failed: $($_.Exception.Message)"
+    }
+
+    if(!$problem){
+      if(!(Get-ChildItem -Force -LiteralPath $DirPath -ErrorAction SilentlyContinue)){
+        return
       }
+      $problem = 'residual files still present after delete (async NTFS delete still finishing?)'
+    }
+
+    if($attempt -lt $MaxAttempts){
+      Write-Host "Wipe attempt $attempt failed ($problem) - retrying in $($DelayMs)ms"
+      Start-Sleep -Milliseconds $DelayMs
+    } else {
+      throw "Wipe of $DirPath did not complete after $MaxAttempts attempts - $problem"
     }
   }
-  throw $failure
 }
 
 if(!(Get-Website -Name $SiteName -ErrorAction SilentlyContinue)){
@@ -106,7 +121,7 @@ if(![string]::IsNullOrWhiteSpace($AdminSiteName) -and (Get-Website -Name $AdminS
 
 if(Test-Path $RemoteDir){
   Write-Host "Wiping $RemoteDir"
-  Remove-DirectoryContentsWithRetry -Path (Join-Path $RemoteDir '*')
+  Remove-DirectoryContentsWithRetry -DirPath $RemoteDir
 } else {
   New-Item -ItemType Directory -Force -Path $RemoteDir | Out-Null
 }