Extract site-specific values to site-config.json

New site-config.json file at C:\Enrollment\ (staged by startnet.cmd from
the enrollment share) contains all West Jefferson-specific values that were
previously hardcoded across 7 scripts. To deploy at a different GE site,
clone site-config.json and change the values - scripts need zero changes.

Config schema (v1.0):
  siteName / siteNameCompact  - UDC/eDNC site args
  urls{}                      - Edge startup tab fallback URLs
  edgeStartupTabs[]           - ordered tab list with .url file basenames
  opentext{}                  - excluded .hep profiles and .lnk shortcuts
  startupItems[]              - Configure-PC toggle list (exe/existing/url)
  taskbarPins[]               - 07-TaskbarLayout pin order with lnk paths
  desktopApps[]               - 06-OrganizeDesktop Phase 2 app list

Every script uses the same inline Get-SiteConfig helper that reads the
JSON and returns $null if missing/corrupt. All consumers fall back to the
current hardcoded West Jefferson defaults when $siteConfig is null, so
PXE servers without a site-config.json continue working identically.

Scripts updated:
  06-OrganizeDesktop.ps1   - desktopApps array from config
  07-TaskbarLayout.ps1     - pinSpec array from config
  08-EdgeDefaultBrowser.ps1 - startup tab loop from config
  Configure-PC.ps1         - startup items + site name from config
  Check-MachineNumber.ps1  - site name from config
  Set-MachineNumber.ps1    - site name from config
  01-eDNC.ps1              - siteName + siteNameCompact from config
  startnet.cmd             - copies site-config.json from enrollment share

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

playbook/shopfloor-setup/Standard/Set-MachineNumber.ps1

@@ -18,10 +18,25 @@
 Add-Type -AssemblyName Microsoft.VisualBasic
 Add-Type -AssemblyName System.Windows.Forms
 
+function Get-SiteConfig {
+    $configPath = 'C:\Enrollment\site-config.json'
+    if (-not (Test-Path -LiteralPath $configPath)) {
+        Write-Host "site-config.json not found - using defaults" -ForegroundColor DarkGray
+        return $null
+    }
+    try {
+        return (Get-Content -LiteralPath $configPath -Raw -ErrorAction Stop | ConvertFrom-Json)
+    } catch {
+        Write-Warning "Failed to parse site-config.json: $_"
+        return $null
+    }
+}
+$siteConfig = Get-SiteConfig
+
 $udcSettingsPath = "C:\ProgramData\UDC\udc_settings.json"
 $udcExePath      = "C:\Program Files\UDC\UDC.exe"
 $ednRegPath      = "HKLM:\SOFTWARE\WOW6432Node\GE Aircraft Engines\DNC\General"
-$site            = "West Jefferson"
+$site            = if ($siteConfig) { $siteConfig.siteName } else { 'West Jefferson' }
 
 # --- Read current values for display ---
 $currentUdc  = $null