feat: Complete DOS machine deployment verification and AD2-NAS sync infrastructure

This checkpoint establishes verified deployment infrastructure for the Dataforth
DOS Update System with proper file synchronization and documentation.

## Key Changes

### TS-4R Backup and Analysis
- Backed up complete TS-4R machine to D:\ClaudeTools\backups\TS-4R\
- Analyzed MENUX.EXE startup menu system (758-line QuickBasic program)
- Documented complete startup sequence: AUTOEXEC.BAT → STARTNET.BAT → MENUX.EXE
- Found MENUX.BAS source code (Feb 2008 version) from KEPCO ABC software archive

### AD2-NAS Sync Infrastructure Fixes
- Created junction: COMMON → _COMMON (single source of truth for software updates)
- Verified bidirectional sync logic prevents data backflow:
  * Test data: DOS → NAS → AD2 → Database (one-way, deleted from NAS)
  * Program updates: AD2 → NAS → DOS (one-way, files remain on AD2)
- Manually deployed correct BAT file versions to NAS after sync connection issues
- Verified all 9 BAT files deployed correctly (5.1KB-8.8KB each)

### Deployment Scripts Created
- check-junction.ps1: Verify COMMON/\_COMMON junction status
- compare-common-folders.ps1: Compare folder contents
- deploy-correct-bat-files.ps1: Deploy BAT files from local to AD2
- fix-common-junction.ps1: Create COMMON → _COMMON junction
- verify-bat-deployment.ps1: Verify file versions on AD2
- manual-push-to-nas.sh: Manual BAT file deployment to NAS
- read-sync-script.ps1: Read Sync-FromNAS.ps1 from AD2
- search-menux-ad2.ps1: Search for MENUX source files

### Documentation Updates
- Updated all deployment guides with MENUX startup sequence
- Added startup flow to credentials.md and session logs
- Documented junction requirement for COMMON/\_COMMON
- Added data flow verification confirming unidirectional sync

## Technical Details

**Files Deployed to NAS (2026-01-20 09:01-09:02):**
- UPDATE.BAT (5,181 bytes) - Machine backup utility
- DEPLOY.BAT (5,579 bytes) - One-time deployment installer
- NWTOC.BAT (6,305 bytes) - Network to Computer updates
- CTONW.BAT (7,831 bytes) - Computer to Network uploads
- CTONWTXT.BAT (1,504 bytes) - Text file version
- CHECKUPD.BAT (6,495 bytes) - Check for updates
- STAGE.BAT (8,794 bytes) - Stage system files
- REBOOT.BAT (5,099 bytes) - Apply staged updates
- AUTOEXEC.BAT (2,211 bytes) - DOS startup configuration

**Sync Logic Verified:**
- PULL: /data/test/TS-*/LOGS/*.DAT copied to AD2, then deleted from NAS
- PUSH: C:\Shares\test\_COMMON\ProdSW\* copied to /data/test/COMMON/ProdSW/
- No reverse flow in either direction (test data never returns to DOS)

**Junction Created:**
- Target: C:\Shares\test\COMMON → C:\Shares\test\_COMMON
- Eliminates duplicate file maintenance
- Backup saved to C:\Shares\test\COMMON.backup

## Files Modified
- DOS_DEPLOYMENT_GUIDE.md: Added automatic startup sequence
- docs/DEPLOYMENT_GUIDE.md: Updated post-reboot expectations
- docs/ENGINEER_HOWTO_GUIDE.md: Added MENUX menu loading step
- credentials.md: Documented startup sequence and MENUX interface
- session-logs/2026-01-19-session.md: Added startup documentation

## Files Added
- 8 PowerShell deployment/verification scripts
- 3 HTML documentation exports
- TS-4R complete backup (not committed to git)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

compare-common-folders.ps1

@@ -0,0 +1,37 @@
+$password = ConvertTo-SecureString 'Paper123!@#' -AsPlainText -Force
+$cred = New-Object System.Management.Automation.PSCredential('INTRANET\sysadmin', $password)
+
+Invoke-Command -ComputerName 192.168.0.6 -Credential $cred -ScriptBlock {
+    Write-Host "=== Files in _COMMON\ProdSW ===" -ForegroundColor Yellow
+    Get-ChildItem "C:\Shares\test\_COMMON\ProdSW" -File |
+        Select-Object Name, Length, LastWriteTime |
+        Sort-Object Name |
+        Format-Table -AutoSize
+    
+    Write-Host ""
+    Write-Host "=== Files in COMMON\ProdSW ===" -ForegroundColor Yellow
+    Get-ChildItem "C:\Shares\test\COMMON\ProdSW" -File |
+        Select-Object Name, Length, LastWriteTime |
+        Sort-Object Name |
+        Format-Table -AutoSize
+    
+    Write-Host ""
+    Write-Host "=== Files ONLY in _COMMON\ProdSW ===" -ForegroundColor Cyan
+    $underFiles = Get-ChildItem "C:\Shares\test\_COMMON\ProdSW" -File | Select-Object -ExpandProperty Name
+    $commonFiles = Get-ChildItem "C:\Shares\test\COMMON\ProdSW" -File | Select-Object -ExpandProperty Name
+    $onlyInUnder = $underFiles | Where-Object { $_ -notin $commonFiles }
+    if ($onlyInUnder) {
+        $onlyInUnder | ForEach-Object { Write-Host "  $_" -ForegroundColor White }
+    } else {
+        Write-Host "  (none)" -ForegroundColor Gray
+    }
+    
+    Write-Host ""
+    Write-Host "=== Files ONLY in COMMON\ProdSW ===" -ForegroundColor Cyan
+    $onlyInCommon = $commonFiles | Where-Object { $_ -notin $underFiles }
+    if ($onlyInCommon) {
+        $onlyInCommon | ForEach-Object { Write-Host "  $_" -ForegroundColor White }
+    } else {
+        Write-Host "  (none)" -ForegroundColor Gray
+    }
+}