Fix UI helper errors during headless -Preset and -Config runs (#4941)

* Make UI helpers no-op when no window exists

The -Preset and -Config paths run Invoke-WinUtilAutoRun before the XAML
form is created and before PresentationCore is loaded, so every call into
Invoke-WPFUIThread failed with InvokeMethodOnNull and every call into
Set-WinUtilTweaksProgressIndicator failed to resolve [Windows.Visibility].
The errors were non-terminating, so tweaks still applied, but each run
filled the log with noise.

Loading presentationframework earlier does not help: Visibility lives in
PresentationCore, which only loads once a WPF object is instantiated, and
the XAML-named progress controls do not exist in these paths either.
Guarding the two helpers covers Invoke-WPFtweaksbutton, Invoke-WPFundoall
and Invoke-WPFFeatureInstall, which the existing per-call-site $hasUI
convention never reached.

* Suppress stray console output from automation runs

Invoke-WPFRunspace returns an IAsyncResult that no caller uses, and
Set-WinUtilRegistry was the only New-PSDrive call site that did not
suppress its output. A GUI click handler discards both, but the -Preset
and -Config paths call the workflows directly, so an async handle dump
and a PSDrive table landed in the user's log.

The handle itself is kept because pester/runspace.Tests.ps1 asserts that
Invoke-WPFRunspace returns a single IAsyncResult, so the suppression goes
at the four call sites reachable from Invoke-WinUtilAutoRun.

* Add project learning for window-free UI helpers

AGENTS.md

@@ -163,6 +163,7 @@ When the user corrects an agent approach, add or tighten one concrete rule here
 - Import Pester 5.8.0 before running tests so `Invoke-Pester -Output Detailed -CI` does not resolve to Windows' inbox Pester 3.4.0.
 - Keep package install/uninstall process launches simple unless explicitly requested; do not add a separate stdout/stderr process logging helper for winget or Chocolatey.
 - When the active log file is owned by `Start-Transcript`, do not call `Add-Content` against that file; write to host output so the transcript captures the line in the same log file without recording a terminating-error diagnostic.
+- Keep UI helpers such as `Invoke-WPFUIThread` and `Set-WinUtilTweaksProgressIndicator` safe to call without a window; the `-Preset` and `-Config` paths run the workflows before the form is created and before PresentationCore is loaded.
 - Log install/uninstall package names and package-manager IDs before queuing background runspace work; do not rely on runspace host output for the package identity.
 - For Win11 Creator, start each new ISO modification in a fresh `WinUtil_Win11ISO_*` temp directory; existing-work detection is only for resuming/exporting already modified media.
 - For Win11 Creator driver injection, keep offline WIM servicing to one mount, one `/Add-Driver`, and one commit; do not export editions or run unrelated WIM cleanup, and reject damaged metadata before ISO export.

functions/private/Set-WinUtilRegistry.ps1

@@ -28,7 +28,7 @@ function Set-WinUtilRegistry {
     )
 
     try {
-        if(!(Test-Path 'HKU:\')) {New-PSDrive -PSProvider Registry -Name HKU -Root HKEY_USERS}
+        if(!(Test-Path 'HKU:\')) {New-PSDrive -PSProvider Registry -Name HKU -Root HKEY_USERS | Out-Null}
 
         If (!(Test-Path $Path)) {
             Write-Host "$Path was not found. Creating..."

functions/private/Set-WinUtilTweaksProgressIndicator.ps1

@@ -18,6 +18,10 @@ function Set-WinUtilTweaksProgressIndicator {
         [int]$Percent
     )
 
+    if ($null -eq $sync.form -or $null -eq $sync.form.Dispatcher) {
+        return
+    }
+
     $indicatorVisible = if ($Visible) { [Windows.Visibility]::Visible } else { [Windows.Visibility]::Collapsed }
     $indicatorLabel = $Label
     $hasLabel = $PSBoundParameters.ContainsKey('Label')

functions/public/Invoke-WPFAppxRemoval.ps1

@@ -96,5 +96,5 @@ function Invoke-WPFAppxRemoval {
             $sync.ProcessRunning = $false
         }
 
-    }
+    } | Out-Null
 }

functions/public/Invoke-WPFFeatureInstall.ps1

@@ -36,5 +36,5 @@ function Invoke-WPFFeatureInstall {
         Write-Host "---   Features are Installed    ---"
         Write-Host "---  A Reboot may be required   ---"
         Write-Host "==================================="
-    }
+    } | Out-Null
 }

functions/public/Invoke-WPFInstall.ps1

@@ -110,5 +110,5 @@ function Invoke-WPFInstall {
             }
             $sync.ProcessRunning = $False
         }
-    }
+    } | Out-Null
 }

functions/public/Invoke-WPFUIThread.ps1

@@ -1,3 +1,7 @@
 function Invoke-WPFUIThread ($ScriptBlock) {
+    if ($null -eq $sync.form -or $null -eq $sync.form.Dispatcher) {
+        return
+    }
+
     $sync.form.Dispatcher.Invoke([action]$ScriptBlock)
 }

functions/public/Invoke-WPFtweaksbutton.ps1

@@ -88,5 +88,5 @@ function Invoke-WPFtweaksbutton {
     Write-Host "--     Tweaks are Finished    ---"
     Write-Host "================================="
     Write-WinUtilLog -Component "Tweaks" -Message "Tweaks workflow completed."
-  }
+  } | Out-Null
 }

pester/headless-ui.Tests.ps1

@@ -0,0 +1,107 @@
+#===========================================================================
+# Tests - UI Helpers During Headless (-Preset / -Config) Runs
+#===========================================================================
+
+BeforeAll {
+    $script:repoRoot = (Resolve-Path (Join-Path $PSScriptRoot "..")).Path
+
+    if (-not ("Windows.Visibility" -as [type])) {
+        Add-Type @"
+namespace Windows
+{
+    public enum Visibility
+    {
+        Visible,
+        Collapsed
+    }
+}
+"@
+    }
+
+    . (Join-Path $script:repoRoot "functions\public\Invoke-WPFUIThread.ps1")
+    . (Join-Path $script:repoRoot "functions\private\Set-WinUtilTweaksProgressIndicator.ps1")
+
+    function script:New-WinUtilFakeForm {
+        $dispatcher = New-Object psobject
+        $dispatcher | Add-Member -MemberType NoteProperty -Name InvokeCount -Value 0
+        $dispatcher | Add-Member -MemberType ScriptMethod -Name Invoke -Value {
+            param($Action)
+
+            $null = $Action
+            $this.InvokeCount++
+        }
+
+        $form = New-Object psobject
+        $form | Add-Member -MemberType NoteProperty -Name Dispatcher -Value $dispatcher
+        return $form
+    }
+
+    function script:New-WinUtilFakeIndicatorControlSet {
+        @{
+            Bar   = [pscustomobject]@{ Visibility = [Windows.Visibility]::Collapsed }
+            Label = [pscustomobject]@{ Text = "" }
+            Value = [pscustomobject]@{ Value = 0 }
+        }
+    }
+}
+
+Describe "Invoke-WPFUIThread without a window" {
+    AfterEach {
+        Remove-Variable -Name sync -Scope Script -ErrorAction SilentlyContinue
+    }
+
+    It "does nothing when the automation paths run before the form is created" {
+        $script:sync = [Hashtable]::Synchronized(@{})
+        $script:blockRan = $false
+
+        { Invoke-WPFUIThread -ScriptBlock { $script:blockRan = $true } } | Should -Not -Throw
+        $script:blockRan | Should -BeFalse
+    }
+
+    It "does nothing when the form exists but has no dispatcher" {
+        $script:sync = [Hashtable]::Synchronized(@{ Form = [pscustomobject]@{ Dispatcher = $null } })
+        $script:blockRan = $false
+
+        { Invoke-WPFUIThread -ScriptBlock { $script:blockRan = $true } } | Should -Not -Throw
+        $script:blockRan | Should -BeFalse
+    }
+
+    It "still marshals onto the dispatcher when a window exists" {
+        $form = New-WinUtilFakeForm
+        $script:sync = [Hashtable]::Synchronized(@{ Form = $form })
+
+        Invoke-WPFUIThread -ScriptBlock { }
+
+        $form.Dispatcher.InvokeCount | Should -Be 1
+    }
+}
+
+Describe "Set-WinUtilTweaksProgressIndicator without a window" {
+    AfterEach {
+        Remove-Variable -Name sync -Scope Script -ErrorAction SilentlyContinue
+    }
+
+    It "returns before resolving WPF types when the form is missing" {
+        $script:sync = [Hashtable]::Synchronized(@{})
+
+        { Set-WinUtilTweaksProgressIndicator -Visible $true -Label "Creating restore point" -Percent 0 } | Should -Not -Throw
+    }
+
+    It "still updates the indicator controls when a window exists" {
+        $controls = New-WinUtilFakeIndicatorControlSet
+        $script:sync = [Hashtable]::Synchronized(@{
+            Form                    = New-WinUtilFakeForm
+            WPFTweaksProgressBar    = $controls.Bar
+            WPFTweaksProgressLabel  = $controls.Label
+            WPFTweaksProgressValue  = $controls.Value
+        })
+
+        Mock Invoke-WPFUIThread { & $ScriptBlock }
+
+        Set-WinUtilTweaksProgressIndicator -Visible $true -Label "Applying WPFTweaksTelemetry (1/17)" -Percent 42
+
+        $controls.Bar.Visibility | Should -Be ([Windows.Visibility]::Visible)
+        $controls.Label.Text | Should -Be "Applying WPFTweaksTelemetry (1/17)"
+        $controls.Value.Value | Should -Be 42
+    }
+}