Machine number input at PXE menu for Standard PCs

Adds a machine number prompt to startnet.cmd after the Standard sub-type
selection. Tech enters the number during the PXE boot process. Defaults
to 9999 if Enter is pressed (existing placeholder behavior).

Written to C:\Enrollment\machine-number.txt alongside pc-type.txt.

Consumers:
  00-PreInstall-MachineApps.ps1 - replaces 9999 in UDC InstallArgs with
    the entered number, so UDC installs with the correct machine number
    from the start (no post-setup Set-MachineNumber needed).
  01-eDNC.ps1 - writes the machine number to the DNC\General\MachineNo
    registry value during eDNC install.
  Configure-PC.ps1 - existing $needsMachineNumber check already skips
    the prompt when UDC/eDNC aren't at 9999, so no change needed.

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

playbook/shopfloor-setup/Standard/01-eDNC.ps1

@@ -61,11 +61,21 @@ foreach ($c in $copies) {
     }
 }
 
-# --- 3. Set DNC site ---
+# --- 3. Set DNC site + machine number ---
 $regBase = "HKLM\SOFTWARE\WOW6432Node\GE Aircraft Engines\DNC"
 reg add "$regBase\General" /v Site /t REG_SZ /d $siteNameCompact /f | Out-Null
 Write-Host "  DNC site set to $siteNameCompact."
 
+# Set machine number if tech entered one during PXE menu (defaults to 9999)
+$machineNumFile = 'C:\Enrollment\machine-number.txt'
+$machineNum = '9999'
+if (Test-Path -LiteralPath $machineNumFile) {
+    $num = (Get-Content -LiteralPath $machineNumFile -First 1 -ErrorAction SilentlyContinue).Trim()
+    if ($num -and $num -match '^\d+$') { $machineNum = $num }
+}
+reg add "$regBase\General" /v MachineNo /t REG_SZ /d $machineNum /f | Out-Null
+Write-Host "  DNC MachineNo set to $machineNum."
+
 # --- 4. Deploy custom eMxInfo.txt to both Program Files paths ---
 if (Test-Path $emxInfo) {
     $dest86 = "C:\Program Files (x86)\DNC\Server Files"