fix(kiosk): keyboard filter covers admins + taskbar auto-hide + disable sm-bootstrap in-session

Live e2e: in the sm-bootstrap session the taskbar showed and Win/Start worked.
- Keyboard Filter EXEMPTS administrators by default and sm-bootstrap is an admin, so
  Win/Start/Alt-Tab etc. were never blocked. Set WEKF_Settings
  DisableKeyboardFilterForAdministrators=false so the filter applies to it.
- Auto-hide the taskbar (default-user StuckRects3, inherited by sm-bootstrap) so it
  doesn't peek over the fullscreen wizard.
- TearDownAsync now Disable-LocalUser's sm-bootstrap in-session (immediate) so it's
  unusable at once; the deferred SYSTEM task still deletes it on next boot (SAM-confirmed
  the delete works now).

Verified: Configure-Kiosk parses under Windows PowerShell 5.1 (ASCII-clean); welcome 29/29.

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

windows/installer/oem/Configure-Kiosk.ps1

@@ -24,11 +24,29 @@ Log 'configuring onboarding lockdown (Explorer shell + policy)'
 # --- Keyboard Filter: block shell/escape hotkeys for the locked-down session ---
 Enable-WindowsOptionalFeature -Online -FeatureName Client-KeyboardFilter -NoRestart -ErrorAction SilentlyContinue | Out-Null
 $kf='root\standardcimv2\embedded'
+# CRITICAL: by default the Keyboard Filter EXEMPTS administrators, and sm-bootstrap is an
+# admin -> Win/Start/etc. were NOT blocked. Turn that exemption off so the filter applies.
+$adm=Get-CimInstance -Namespace $kf -ClassName WEKF_Settings -Filter "Name='DisableKeyboardFilterForAdministrators'" -ErrorAction SilentlyContinue
+if($adm){ $adm.Value='false'; Set-CimInstance -InputObject $adm -ErrorAction SilentlyContinue }
 foreach($combo in 'Win','Win+L','Ctrl+Esc','Ctrl+Win+F','Win+R','Alt+Tab','Ctrl+Shift+Esc','Alt+F4'){
     $p=Get-CimInstance -Namespace $kf -ClassName WEKF_PredefinedKey -Filter "Id='$combo'" -ErrorAction SilentlyContinue
     if($p){ $p.Enabled=$true; Set-CimInstance -InputObject $p -ErrorAction SilentlyContinue }
 }
-Log 'keyboard filter rules enabled'
+Log 'keyboard filter rules enabled (admins included)'
+
+# --- Hide the taskbar for the locked-down session (auto-hide in the default-user hive,
+#     which the sm-bootstrap profile inherits). The fullscreen wizard covers it, but
+#     auto-hide stops it peeking. StuckRects3 byte 8: 0x03 = auto-hide on. ---
+try {
+    & reg load 'HKLM\SM_DU_TB' 'C:\Users\Default\NTUSER.DAT' 2>$null | Out-Null
+    $sr='HKLM:\SM_DU_TB\Software\Microsoft\Windows\CurrentVersion\Explorer\StuckRects3'
+    New-Item $sr -Force | Out-Null
+    $bytes=[byte[]](0x30,0x00,0x00,0x00,0x28,0x00,0x00,0x00,0x03,0x00,0x00,0x00,0x30,0x00,0x00,0x00,
+                    0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
+                    0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00)
+    Set-ItemProperty $sr -Name 'Settings' -Value $bytes -Type Binary
+} catch {} finally { [gc]::Collect(); Start-Sleep -Milliseconds 300; & reg unload 'HKLM\SM_DU_TB' 2>$null | Out-Null }
+Log 'taskbar auto-hide set for default user'
 
 # --- escape policies (machine-wide; reverted at teardown) ---
 $sys='HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System'

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

@@ -40,7 +40,10 @@ public sealed class BootstrapService(IProcessRunner runner) : IBootstrapService
         // 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 unregisters itself.
-        await Ps($"Remove-LocalUser -Name '{u}' -EA SilentlyContinue", ct);
+        // Disable immediately (in-session, takes effect at once so the account is unusable
+        // and shows as disabled), then best-effort delete; the deferred task does the real
+        // delete on next boot when it isn't logged on.
+        await Ps($"Disable-LocalUser -Name '{u}' -EA SilentlyContinue; 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; " +