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/06-OrganizeDesktop.ps1

@@ -319,12 +319,20 @@ function Add-ShopfloorToolsApps {
             'existing' {
                 $src = Find-ExistingLnk $app.SourceName
                 if ($src) {
-                    if (-not (& $ensureToolsDir)) { break }
-                    try {
-                        Copy-Item -LiteralPath $src -Destination $dest -Force -ErrorAction Stop
-                        Write-Host "  copied:  $($app.Name) from $src"
-                    } catch {
-                        Write-Warning "Failed to copy $src -> $dest : $_"
+                    # Skip if the sweep already moved the source into the
+                    # destination folder (src == dest → "cannot overwrite
+                    # the item with itself").
+                    if ((Resolve-Path -LiteralPath $src -ErrorAction SilentlyContinue).Path -eq
+                        (Join-Path $shopfloorToolsDir $app.SourceName)) {
+                        Write-Host "  exists:  $($app.Name) (already in Shopfloor Tools)"
+                    } else {
+                        if (-not (& $ensureToolsDir)) { break }
+                        try {
+                            Copy-Item -LiteralPath $src -Destination $dest -Force -ErrorAction Stop
+                            Write-Host "  copied:  $($app.Name) from $src"
+                        } catch {
+                            Write-Warning "Failed to copy $src -> $dest : $_"
+                        }
                     }
                 } else {
                     Write-Host "  skip:    $($app.Name) - no source .lnk found" -ForegroundColor DarkGray