fix: Replace NUL device references with DOS 6.22 compatible tests

Critical fix for DOS 6.22 compatibility - NUL is a reserved device name
in both DOS and Windows and cannot be used as a file/directory name.

Problem:
- "T: 2>NUL" attempts to create a file called "NUL" (not allowed)
- "IF NOT EXIST T:\NUL" tests for NUL device (unreliable)
- "IF NOT EXIST path\NUL" treats NUL as filename (invalid)

Solution - Replaced with proper DOS 6.22 tests:
- "T: 2>NUL" → "DIR T:\ >nul" (test drive access via directory listing)
- "IF NOT EXIST T:\NUL" → "IF NOT EXIST T:\*.*" (test for any files)
- "IF NOT EXIST path\NUL" → "IF NOT EXIST path\*.*" (test directory)

Note: Using lowercase "nul" for output redirection is acceptable as
it redirects to the NUL device, but NUL as a filename/path is invalid.

Files updated:
- DEPLOY.BAT: Fixed drive and directory tests
- UPDATE.BAT: Fixed drive and directory tests
- NWTOC.BAT: Fixed drive and directory tests
- CTONW.BAT: Fixed drive and directory tests
- CHECKUPD.BAT: Fixed drive and directory tests
- DOSTEST.BAT: Fixed drive and directory tests

Created fix-nul-references.ps1:
- Automated script to find and fix NUL references
- Preserves CRLF line endings
- Updates all BAT files consistently

Created monitoring scripts:
- monitor-sync-status.ps1: Periodic sync monitoring
- quick-sync-check.ps1: Quick AD2-to-NAS sync status check

Verification:
- All BAT files maintain CRLF line terminators
- File sizes increased slightly (4-8 bytes) due to pattern changes
- DOS 6.22 compatible wildcard tests (*.*) used throughout

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

monitor-sync-status.ps1

@@ -0,0 +1,76 @@
+# Monitor AD2-to-NAS sync status periodically
+
+param(
+    [int]$Checks = 5,
+    [int]$IntervalMinutes = 3
+)
+
+$Username = "INTRANET\sysadmin"
+$Password = ConvertTo-SecureString "Paper123!@#" -AsPlainText -Force
+$Cred = New-Object System.Management.Automation.PSCredential($Username, $Password)
+
+Write-Host "========================================" -ForegroundColor Cyan
+Write-Host "AD2-to-NAS Sync Monitor" -ForegroundColor Cyan
+Write-Host "========================================" -ForegroundColor Cyan
+Write-Host "Checks: $Checks (every $IntervalMinutes minutes)"
+Write-Host "Monitoring CRLF preservation on synced files"
+Write-Host ""
+
+for ($i = 1; $i -le $Checks; $i++) {
+    $Timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
+    Write-Host "[$Timestamp] Check $i of $Checks" -ForegroundColor Yellow
+    Write-Host "----------------------------------------"
+
+    # Check AD2 sync log (last 10 lines)
+    try {
+        $LogTail = Invoke-Command -ComputerName 192.168.0.6 -Credential $Cred -ScriptBlock {
+            Get-Content 'C:\Shares\test\scripts\sync-from-nas.log' -Tail 10
+        }
+
+        Write-Host "[INFO] Recent sync log entries:"
+        $LogTail | ForEach-Object { Write-Host "  $_" }
+        Write-Host ""
+
+    } catch {
+        Write-Host "[ERROR] Could not read AD2 sync log: $_" -ForegroundColor Red
+        Write-Host ""
+    }
+
+    # Check NAS file timestamps and CRLF
+    Write-Host "[INFO] Checking DEPLOY.BAT on NAS..."
+    $NASInfo = & 'C:\Windows\System32\OpenSSH\ssh.exe' -o BatchMode=yes root@192.168.0.9 'ls -la /data/test/DEPLOY.BAT' 2>&1
+
+    if ($LASTEXITCODE -eq 0) {
+        Write-Host "  $NASInfo"
+
+        # Copy and verify CRLF
+        & 'C:\Windows\System32\OpenSSH\scp.exe' -O root@192.168.0.9:/data/test/DEPLOY.BAT ./DEPLOY_MONITOR.BAT 2>$null
+
+        if (Test-Path "DEPLOY_MONITOR.BAT") {
+            $Content = Get-Content "DEPLOY_MONITOR.BAT" -Raw
+            $Size = (Get-Item "DEPLOY_MONITOR.BAT").Length
+
+            if ($Content -match "`r`n") {
+                Write-Host "  [SUCCESS] CRLF preserved ($Size bytes)" -ForegroundColor Green
+            } else {
+                Write-Host "  [WARNING] LF only ($Size bytes)" -ForegroundColor Yellow
+            }
+
+            Remove-Item "DEPLOY_MONITOR.BAT" -Force
+        }
+    } else {
+        Write-Host "  [ERROR] Could not access NAS" -ForegroundColor Red
+    }
+
+    Write-Host ""
+
+    if ($i -lt $Checks) {
+        Write-Host "Waiting $IntervalMinutes minutes until next check..."
+        Write-Host ""
+        Start-Sleep -Seconds ($IntervalMinutes * 60)
+    }
+}
+
+Write-Host "========================================" -ForegroundColor Cyan
+Write-Host "Monitoring Complete" -ForegroundColor Cyan
+Write-Host "========================================" -ForegroundColor Cyan