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/startnet.cmd

@@ -216,6 +216,14 @@ if not exist W:\Windows\System32\config\system goto wait_enroll
 echo Found Windows at W:
 mkdir W:\Enrollment 2>NUL
 
+REM --- Copy site config (drives site-specific values in all setup scripts) ---
+if exist "Y:\site-config.json" (
+    copy /Y "Y:\site-config.json" "W:\Enrollment\site-config.json"
+    echo Copied site-config.json.
+) else (
+    echo WARNING: site-config.json not found on enrollment share.
+)
+
 REM --- Copy PPKG if selected ---
 if "%PPKG%"=="" goto copy_pctype
 copy /Y "Y:\%PPKG%" "W:\Enrollment\%PPKG%"