fix(welcome): harden kiosk chrome + add startup/WebView2 diagnostics

4th VM e2e: kiosk shell engages + the app launches fullscreen, but the Blazor
wizard renders BLANK and the kiosk chrome didn't apply (title bar present) — the
app didn't crash, so there's no log to read. Two changes:

1) ApplyKioskChrome made defensive (null-guard HWND/AppWindow, FullScreen presenter
   only, returns bool) and wrapped in try/catch at the call site, so a chrome
   failure can never stall app/WebView startup (the likely cause of the blank).
2) Always-on file log at C:\ProgramData\SilverMetal\welcome.log: app ctor, window
   create, chrome result, unhandled exceptions, and the BlazorWebView/WebView2
   lifecycle (Initialized, NavigationCompleted, ProcessFailed). If the wizard is
   still blank next run, this pinpoints whether WebView2 env creation failed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

windows/welcome/src/SilverOS.Welcome.App/App.xaml.cs

@@ -1,20 +1,40 @@
-namespace SilverOS.Welcome.App;
+namespace SilverOS.Welcome.App;
 
 public partial class App : Application
 {
 	public App()
 	{
+		Diag.Log("App ctor");
+		AppDomain.CurrentDomain.UnhandledException += (s, e) =>
+			Diag.Log("UNHANDLED: " + (e.ExceptionObject as Exception)?.ToString());
+		TaskScheduler.UnobservedTaskException += (s, e) =>
+		{
+			Diag.Log("UNOBSERVED TASK: " + e.Exception);
+			e.SetObserved();
+		};
 		InitializeComponent();
 	}
 
 	protected override Window CreateWindow(IActivationState? activationState)
 	{
+		Diag.Log("CreateWindow");
 		var window = new Window(new MainPage()) { Title = "SilverMetal Windows" };
 #if WINDOWS
+		// Apply kiosk chrome once the native window handler exists. Wrapped so a
+		// chrome failure can NEVER break app/WebView startup (a previous version
+		// threw here and left the wizard blank). HandlerChanged can fire before the
+		// HWND is ready, so ApplyKioskChrome null-guards and re-applies safely.
 		window.HandlerChanged += (s, e) =>
 		{
-			if (window.Handler?.PlatformView is Microsoft.UI.Xaml.Window native)
-				native.ApplyKioskChrome();
+			try
+			{
+				if (window.Handler?.PlatformView is Microsoft.UI.Xaml.Window native)
+				{
+					var ok = native.ApplyKioskChrome();
+					Diag.Log($"ApplyKioskChrome applied={ok}");
+				}
+			}
+			catch (Exception ex) { Diag.Log("ApplyKioskChrome FAILED: " + ex); }
 		};
 #endif
 		return window;

windows/welcome/src/SilverOS.Welcome.App/Diagnostics.cs

@@ -0,0 +1,24 @@
+namespace SilverOS.Welcome.App;
+
+// Lightweight always-on file logger for first-boot diagnosis. The Welcome app
+// runs as the kiosk shell with no console and (in Release) no debugger, so when
+// something fails silently (blank WebView, chrome not applied) there is nowhere
+// to look. This writes to a world-writable ProgramData path that survives the
+// session and can be read off the disk image.
+public static class Diag
+{
+    const string Dir = @"C:\ProgramData\SilverMetal";
+    const string Path = Dir + @"\welcome.log";
+    static readonly object _lock = new();
+
+    public static void Log(string msg)
+    {
+        try
+        {
+            System.IO.Directory.CreateDirectory(Dir);
+            lock (_lock)
+                System.IO.File.AppendAllText(Path, $"{DateTime.Now:HH:mm:ss.fff} {msg}{Environment.NewLine}");
+        }
+        catch { /* logging must never throw */ }
+    }
+}

windows/welcome/src/SilverOS.Welcome.App/MainPage.xaml

@@ -1,11 +1,13 @@
-<?xml version="1.0" encoding="utf-8" ?>
+<?xml version="1.0" encoding="utf-8" ?>
 <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              xmlns:local="clr-namespace:SilverOS.Welcome.App"
              xmlns:components="clr-namespace:SilverOS.Welcome.App.Components;assembly=SilverOS.Welcome.UI"
              x:Class="SilverOS.Welcome.App.MainPage">
 
-    <BlazorWebView x:Name="blazorWebView" HostPage="wwwroot/index.html">
+    <BlazorWebView x:Name="blazorWebView" HostPage="wwwroot/index.html"
+                   BlazorWebViewInitialized="OnBlazorInitialized"
+                   UrlLoading="OnUrlLoading">
         <BlazorWebView.RootComponents>
             <RootComponent Selector="#app" ComponentType="{x:Type components:Routes}" />
         </BlazorWebView.RootComponents>

windows/welcome/src/SilverOS.Welcome.App/MainPage.xaml.cs

@@ -1,9 +1,34 @@
-namespace SilverOS.Welcome.App;
+using Microsoft.AspNetCore.Components.WebView;
+
+namespace SilverOS.Welcome.App;
 
 public partial class MainPage : ContentPage
 {
 	public MainPage()
 	{
 		InitializeComponent();
+		Diag.Log("MainPage ctor");
 	}
+
+	// Fires once the platform WebView2 is created. If this never appears in the log,
+	// WebView2 environment creation failed (the real cause of a blank wizard).
+	void OnBlazorInitialized(object? sender, BlazorWebViewInitializedEventArgs e)
+	{
+		Diag.Log("BlazorWebViewInitialized");
+#if WINDOWS
+		try
+		{
+			var wv = e.WebView; // Microsoft.UI.Xaml.Controls.WebView2
+			wv.NavigationCompleted += (a, b) =>
+				Diag.Log($"WV2 NavigationCompleted ok={b.IsSuccess} status={b.WebErrorStatus}");
+			if (wv.CoreWebView2 is not null)
+				wv.CoreWebView2.ProcessFailed += (a, b) =>
+					Diag.Log("WV2 ProcessFailed: " + b.ProcessFailedKind);
+		}
+		catch (Exception ex) { Diag.Log("WV2 hook failed: " + ex.Message); }
+#endif
+	}
+
+	void OnUrlLoading(object? sender, UrlLoadingEventArgs e)
+		=> Diag.Log("UrlLoading: " + e.Url);
 }

windows/welcome/src/SilverOS.Welcome.App/Platforms/Windows/WindowExtensions.cs

@@ -7,20 +7,21 @@ namespace SilverOS.Welcome.App;
 
 public static class WindowExtensions
 {
-    // Borderless, fullscreen, non-closable kiosk window.
-    public static void ApplyKioskChrome(this Microsoft.UI.Xaml.Window winuiWindow)
+    // Borderless, fullscreen, non-closable kiosk window. Returns true when applied.
+    // Defensive: HandlerChanged can fire before the HWND/AppWindow is ready, so we
+    // bail out cleanly and rely on a later HandlerChanged to apply it.
+    public static bool ApplyKioskChrome(this Microsoft.UI.Xaml.Window winuiWindow)
     {
         var hwnd = WindowNative.GetWindowHandle(winuiWindow);
+        if (hwnd == IntPtr.Zero) return false;
         var id = Win32Interop.GetWindowIdFromWindow(hwnd);
         var appWindow = AppWindow.GetFromWindowId(id);
-        if (appWindow.Presenter is OverlappedPresenter p)
-        {
-            p.SetBorderAndTitleBar(false, false);
-            p.IsResizable = false; p.IsMaximizable = false; p.IsMinimizable = false;
-        }
+        if (appWindow is null) return false;
+        // FullScreen presenter is borderless (no title bar) by nature — simpler and
+        // more reliable than toggling OverlappedPresenter border/title-bar flags.
         appWindow.SetPresenter(AppWindowPresenterKind.FullScreen);
-        // Block the close box; the wizard exits by rebooting, not by closing.
         appWindow.Closing += (s, e) => e.Cancel = true;
+        return true;
     }
 }
 #endif