fix(first-boot): re-apply personalization branding online + defer sm-bootstrap cleanup

VM e2e findings on the real-user desktop:
1. Lock/login screen + wallpaper NOT branded (OEM About WAS) — Windows resets the
   offline-baked personalization (PersonalizationCSP / default-user wallpaper / FVE)
   during OOBE, same class as the UAC reset. Fix: stage windows/branding/ into the
   image and re-run Apply-Branding -Mode Online from SetupComplete (post-OOBE, as
   SYSTEM) where it sticks. OEM About re-asserted harmlessly.
2. sm-bootstrap account still present after onboarding — TearDownAsync's in-session
   Remove-LocalUser no-ops (can't delete the account you're logged in as). Fix: keep
   the best-effort in-session attempt, but DEFER the real removal to a SYSTEM
   AtStartup scheduled task that runs on next boot (sm-bootstrap not logged on),
   removes the account + Win32_UserProfile, then deletes itself.

(Network 'no adapter' in the VM was a Proxmox NIC-model regression to virtio — fixed
by switching the VM to Intel e1000; not a SilverMetal change.)

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

windows/installer/build.ps1

@@ -234,6 +234,11 @@ function Invoke-ServiceWim {
         Copy-Item (Join-Path $PSScriptRoot 'oem\SetupComplete.cmd') $scripts -Force
         Copy-Item (Join-Path $PSScriptRoot 'oem\Configure-Kiosk.ps1') $scripts -Force
         Copy-Item (Join-Path $WindowsDir 'hardening\*') (Join-Path $scripts 'hardening') -Recurse -Force
+        # Stage the branding module so SetupComplete.cmd can re-apply branding ONLINE
+        # (Windows resets the offline personalization bake during OOBE).
+        $brandDest = Join-Path $scripts 'branding'
+        $null = New-Item -ItemType Directory -Force $brandDest
+        Copy-Item (Join-Path $WindowsDir 'branding\*') $brandDest -Recurse -Force
 
         # Stage Welcome app + flavours while the WIM is still mounted.
         Copy-WelcomePayload

windows/installer/oem/SetupComplete.cmd

@@ -14,6 +14,14 @@ set HARD=C:\Windows\Setup\Scripts\hardening
 
 echo [%DATE% %TIME%] SilverMetal first-boot start >> "%LOG%"
 
+REM Re-apply branding ONLINE (lock screen / wallpaper / OEM / FVE). Windows resets
+REM the offline-baked personalization during OOBE, so re-assert it here (post-OOBE,
+REM as SYSTEM) where it sticks. Idempotent with the offline bake.
+if exist "%~dp0branding\Apply-Branding.ps1" (
+  echo [%DATE% %TIME%] re-applying SilverMetal branding (online) >> "%LOG%"
+  powershell -NoProfile -ExecutionPolicy Bypass -File "%~dp0branding\Apply-Branding.ps1" -Mode Online >> "%LOG%" 2>&1
+)
+
 if exist "C:\Program Files\SilverOS\Welcome\SilverOS.Welcome.App.exe" (
   echo [%DATE% %TIME%] configuring onboarding kiosk >> "%LOG%"
   powershell -NoProfile -ExecutionPolicy Bypass -File "%~dp0Configure-Kiosk.ps1" >> "%LOG%" 2>&1

windows/welcome/src/SilverOS.Welcome.Core/Apply/BootstrapService.cs

@@ -36,7 +36,19 @@ public sealed class BootstrapService(IProcessRunner runner) : IBootstrapService
                  $"Remove-ItemProperty -Path {w} -Name DefaultUserName -EA SilentlyContinue; " +
                  $"Remove-ItemProperty -Path {w} -Name DefaultDomainName -EA SilentlyContinue", ct);
         var u = Esc(bootstrapUser);
+        // Best-effort in-session removal (usually no-ops — you can't delete the account
+        // you're logged in as), THEN defer the real removal to a SYSTEM startup task that
+        // runs on next boot, when sm-bootstrap is no longer logged on. It removes the
+        // account + profile, then deletes itself. Encoded command avoids schtasks quoting.
         await Ps($"Remove-LocalUser -Name '{u}' -EA SilentlyContinue", ct);
+        var cleanup =
+            $"Remove-LocalUser -Name '{u}' -ErrorAction SilentlyContinue; " +
+            $"Get-CimInstance Win32_UserProfile | Where-Object {{ $_.LocalPath -like '*\\{u}' }} | Remove-CimInstance -ErrorAction SilentlyContinue; " +
+            "schtasks /delete /tn 'SilverMetalBootstrapCleanup' /f";
+        var b64 = Convert.ToBase64String(System.Text.Encoding.Unicode.GetBytes(cleanup));
+        await Ps("schtasks /create /tn 'SilverMetalBootstrapCleanup' " +
+                 $"/tr 'powershell -NoProfile -ExecutionPolicy Bypass -EncodedCommand {b64}' " +
+                 "/sc onstart /ru SYSTEM /rl HIGHEST /f", ct);
     }
     private static string Esc(string s) => s.Replace("'", "''");
     private Task Ps(string s, CancellationToken ct) =>