Fix 5 bugs from shopfloor-setup transcript review

1. UDC JSON ACL: set on directory C:\ProgramData\UDC\ with
   ContainerInherit+ObjectInherit instead of the file. UDC_Setup.exe
   gets killed by KillAfterDetection before UDC.exe creates
   udc_settings.json, so the file doesn't exist at ACL-grant time.
   Directory-level ACL with inheritance covers any file created later.

2. Set-MachineNumber.ps1 auto-running: the type-specific loop's
   Get-ChildItem -Filter "*.ps1" picked up the desktop tool alongside
   the numbered installer scripts. Added Where-Object { $_.Name -match
   '^\d' } so only numbered-prefix scripts (01-eDNC, 02-ACLs) run.

3. WJ Shopfloor copy-to-self: Phase 1 sweep moved WJ Shopfloor.lnk
   into Shopfloor Tools\, then Phase 2's Find-ExistingLnk found it
   there and tried to Copy-Item to the same path. Now checks if
   resolved source path == destination and prints "exists: (already
   in Shopfloor Tools)" instead of erroring.

4. NTLARS missing from taskbar pins: the $pinSpec entry was never
   added to 07-TaskbarLayout.ps1 despite the comment update. Added
   between eDNC and Defect_Tracker in pin order.

5. shutdown /a stderr noise: 15+ red "Unable to abort system shutdown"
   lines in the transcript from shutdown.exe writing to stderr when no
   shutdown is pending. Changed all occurrences in Run-ShopfloorSetup,
   00-PreInstall-MachineApps to: cmd /c "shutdown /a 2>nul" *>$null
   which suppresses both native stderr and PS error stream.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

playbook/shopfloor-setup/Shopfloor/00-PreInstall-MachineApps.ps1

@@ -151,7 +151,7 @@ foreach ($app in $config.Applications) {
     # Cancel any reboot a previous installer scheduled (some respect /norestart, some
     # don't - VC++ 2008's bootstrapper sometimes triggers an immediate Windows reboot
     # despite the flag). Doing this BEFORE each install protects the rest of the loop.
-    & shutdown.exe /a 2>$null
+    cmd /c "shutdown /a 2>nul" *>$null
 
     Write-PreInstallLog "==> $($app.Name)"
 
@@ -369,6 +369,6 @@ Write-PreInstallLog "============================================"
 # Final reboot cancel - if the last installer in the loop scheduled one, the
 # dispatcher's later `shutdown /a` won't fire until the next baseline script starts.
 # Cancel here so control returns cleanly to Run-ShopfloorSetup.ps1.
-& shutdown.exe /a 2>$null
+cmd /c "shutdown /a 2>nul" *>$null
 
 exit 0