added upsate script

docs/WINDOWS_AGENT_UPDATE_BAT.md

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+# Windows Agent Update BAT
+
+Workspace reference: [`GSP-WORKSPACE.md`](../../GSP-WORKSPACE.md)
+
+## Purpose
+
+`Update-Agent.bat` updates the Git-managed GSP Windows Agent repository, stops the agent first, and starts it again after the update.
+
+It is intentionally small and local:
+
+- no Task Scheduler changes
+- no installer execution
+- no customer data cleanup
+- no deletion of game server folders, configs, logs, or Workshop data
+
+## File location
+
+Place `Update-Agent.bat` in the repository root:
+
+- example checkout: `C:\GSP\windows-agent\Update-Agent.bat`
+
+The current repository layout expects the managed start and stop launchers here:
+
+- `OGP64\agent_start.bat`
+- `OGP64\agent_stop.bat`
+
+If those are missing, the updater tries the obvious fallback launchers:
+
+- `OGP64\OGP\Install\agent_start.bat`
+- `OGP64\OGP\Install\agent_stop.bat`
+
+## How to run it
+
+1. Right-click `Update-Agent.bat`.
+2. Choose `Run as Administrator`.
+3. Review the console output.
+4. Press a key at the end so the window closes only after you read the result.
+
+## How it works
+
+The script:
+
+1. verifies Administrator privileges
+2. verifies the agent repository path
+3. verifies `.git` exists
+4. verifies `git` is available
+5. stops the agent with the existing stop BAT if available
+6. runs `git fetch origin`
+7. runs `git reset --hard origin/unstable`
+8. starts the agent with the existing start BAT if available
+9. pauses so the operator can read any errors
+
+## Editable variables
+
+At the top of `Update-Agent.bat`:
+
+- `AGENT_DIR`
+- `BRANCH`
+- `START_BAT`
+- `STOP_BAT`
+
+Default branch:
+
+- `unstable`
+
+## Changing branch
+
+Edit:
+
+```bat
+set "BRANCH=unstable"
+```
+
+to another remote branch name if needed.
+
+The script resets to:
+
+```bat
+origin/%BRANCH%
+```
+
+## Relationship to start and stop BAT files
+
+`Update-Agent.bat` does not replace the existing launchers.
+
+It reuses:
+
+- `OGP64\agent_stop.bat`
+- `OGP64\agent_start.bat`
+
+That keeps update behavior aligned with the normal manual agent lifecycle.
+
+## Task Scheduler note
+
+This task does not modify Task Scheduler.
+
+The agent can still be configured separately to start at boot through Task Scheduler. `Update-Agent.bat` is a manual administrative update helper, not a scheduled task installer.
+
+## What should stay outside the Git-managed directory
+
+Do not place customer-owned runtime data inside the Git checkout if you want updates to remain low-risk.
+
+Keep these outside the Git-managed repository when possible:
+
+- hosted game server folders
+- save files
+- customer uploads
+- customer scripts
+- customer configs
+- logs you want preserved independently of code updates
+
+The repository should contain the Windows agent code and bundled runtime files, not mutable customer data.
+
+## Assumptions
+
+- The Git checkout root is the correct update boundary.
+- The active branch should be `unstable` by default.
+- The existing root launchers under `OGP64\` are the preferred lifecycle scripts.