fix: Remove all non-DOS 6.22 commands from batch files

Critical compatibility fixes - DOS 6.22 does not support many Windows
batch file features. Removed all incompatible commands and replaced
with DOS 6.22 compatible alternatives.

Issues Fixed:

1. DEPLOY.BAT - Removed SET /P (interactive input)
   - Changed from: SET /P MACHINE=Machine name:
   - Changed to: SET MACHINE=%1 (command-line parameter)
   - Usage: DEPLOY.BAT TS-4R
   - DOS 6.22 does not support SET /P

2. CHECKUPD.BAT - Removed SET /A (arithmetic) and GOTO :EOF
   - Removed 6 instances of SET /A counter arithmetic
   - Replaced numeric counters with flag variables
   - Changed from: SET /A COMMON=COMMON+1
   - Changed to: SET COMMON=FOUND
   - Replaced GOTO :EOF with actual labels
   - Changed display from counts to status messages

3. STAGE.BAT - Removed FOR /F (file parsing)
   - Changed from: FOR /F "skip=1 delims=" %%L IN (...) DO
   - Changed to: TYPE C:\AUTOEXEC.BAT >> C:\AUTOEXEC.TMP
   - DOS 6.22 only supports simple FOR loops

Created check-dos-compatibility.ps1:
- Automated scanner for DOS 6.22 incompatible commands
- Checks for: SET /P, SET /A, IF /I, FOR /F, FOR /L, FOR /R,
  GOTO :EOF, %COMPUTERNAME%, &&, ||, START, invalid NUL usage
- Scans all BAT files and reports line numbers
- Essential for preventing future compatibility issues

Verification:
- All files maintain CRLF line terminators
- All commands tested for DOS 6.22 compatibility
- No SET /A, SET /P, FOR /F, GOTO :EOF remaining
- CHOICE commands retained (CHOICE.COM exists in DOS 6.22)

Impact:
- DEPLOY.BAT now requires parameter: DEPLOY.BAT TS-4R
- CHECKUPD.BAT shows "Updates available" vs exact counts
- STAGE.BAT copies all AUTOEXEC lines (duplicate @ECHO OFF harmless)

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

DEPLOY.BAT

@@ -105,40 +105,40 @@ PAUSE Press any key to exit...
 GOTO END
 
 REM ==================================================================
-REM STEP 3: Get machine name from user
+REM STEP 3: Get machine name from command line
 REM ==================================================================
 
 :GET_MACHINE_NAME
 ECHO [STEP 3/5] Configure machine name...
 ECHO.
-ECHO Enter this machine's name (e.g., TS-4R, TS-7A, TS-12B):
-ECHO.
-ECHO Machine name must match the folder on T: drive.
-ECHO Example: If this is TS-4R, there should be T:\TS-4R\
-ECHO.
-SET /P MACHINE=Machine name:
 
-REM Validate machine name was entered
-IF "%MACHINE%"=="" GOTO MACHINE_NAME_EMPTY
+REM Check if machine name provided as parameter
+IF "%1"=="" GOTO MACHINE_NAME_MISSING
 
-ECHO.
-ECHO [OK] Machine name: %MACHINE%
+SET MACHINE=%1
+ECHO Machine name: %MACHINE%
 ECHO.
 
 REM Verify machine folder exists on network
 ECHO Checking for T:\%MACHINE%\ folder...
-IF NOT EXIST T:\%MACHINE%\NUL MD T:\%MACHINE%
-IF NOT EXIST T:\%MACHINE%\NUL GOTO MACHINE_FOLDER_ERROR
+IF NOT EXIST T:\%MACHINE%\*.* MD T:\%MACHINE%
+IF NOT EXIST T:\%MACHINE%\*.* GOTO MACHINE_FOLDER_ERROR
 
 ECHO [OK] Machine folder ready: T:\%MACHINE%\
 ECHO.
 GOTO BACKUP_AUTOEXEC
 
-:MACHINE_NAME_EMPTY
+:MACHINE_NAME_MISSING
+ECHO [ERROR] Machine name not provided
 ECHO.
-ECHO [ERROR] Machine name cannot be empty
+ECHO Usage:  DEPLOY.BAT machine-name
+ECHO Example: DEPLOY.BAT TS-4R
 ECHO.
-GOTO GET_MACHINE_NAME
+ECHO Machine name must match folder on T: drive.
+ECHO Example: If this is TS-4R, T:\TS-4R\ must exist
+ECHO.
+PAUSE Press any key to exit...
+GOTO END
 
 :MACHINE_FOLDER_ERROR
 ECHO.