Option to render numstat as a prefix in the files panel

When `showNumstatInFilesView` is enabled, the `+N -M` counts render after the filename. In narrow panels (tmux splits, side docks, etc.), the filename takes most of the width and the numstat falls off the right edge, so the feature stops being visible exactly when you want it.

Could there be an option to put numstat before the filename instead? Something like:

```yaml
gui:
numstatPosition: prefix # default: suffix
```

Prefix position would stay visible regardless of filename length, since the counts are short and fixed-width.