Example.png is tracked, which prevents updating if deleted

### Custom Node Testing

- [ ] I have tried disabling custom nodes and the issue persists (see [how to disable custom nodes](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled) if you need help)

### Expected Behavior

output and input folders should ideally be created on installation (or an otherwise inconspicuous .keeper file put in them). That way, if we don't want the Example.png input image, we can delete it without breaking the ability to update. Example.png should probably be placed in a utility repo or alternate cdn and downloaded that way, making it completely optional.

### Actual Behavior

Deleting or removing input/example.png from the repository (a tracked git file) blocks users from updating or pulling changes. Git operations such as pull or merge fail until the file is restored. This leads to update failures for users who have removed the example image, even though it's just an example file.

### Steps to Reproduce

1. Remove Example.png from the input folder (or any changes to tracked files)
2. Run `git pull`.

### Debug Logs

```powershell
➜ ComfyUI git:(c2d7f07d) rm input/example.png
➜ ComfyUI git:(c2d7f07d) ✗ git pull
error: cannot pull with rebase: You have unstaged changes.
error: Please commit or stash them.
➜ ComfyUI git:(c2d7f07d) ✗
```

### Other

_No response_