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>

DOS_DEPLOYMENT_GUIDE.md

@@ -188,10 +188,12 @@ Next Steps:
 1. REBOOT this machine to activate MACHINE variable
    Press Ctrl+Alt+Del to reboot
 
-2. After reboot, run NWTOC to download all updates:
-   C:\BAT\NWTOC
+2. After reboot, system will automatically:
+   - Start network (STARTNET.BAT)
+   - Download updates (NWTOC.BAT runs automatically)
+   - Load test menu (MENUX.EXE)
 
-3. Create initial backup:
+3. Create initial backup when convenient:
    C:\BAT\UPDATE
 
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