Ability to disable opening the file when selecting widget from Widget Explorer

In VS Code, when I am only interested in viewing the widget in the Layout Explorer, opening the file takes a lot of space + it moves all panes in undesirable way.

It'd be nice to have a way to disable the `file opener` or have a separate action to open the file (right click menu or cmd+click combination).

```
devtools version: 2.25.0
VS Code version: 1.83.1
Dart extension: v3.74.0
```

Start by tracing the Widget Explorer's file opener behavior in the Dart DevTools codebase and review the issue discussion for the expected interaction. Compare disabling the opener with a separate open-file action, then verify that selecting a widget can leave the Layout Explorer panes undisturbed while the file remains available through the chosen action.

Written by the indexing model from the issue text.