In a validator app, how to keep focus on the content you’re validating?

I've got a specialized text validation application where the user can either type, copy/paste the text or load file in - then hit Validate for the screen to transition to the results area. Here's a demo. If you click on an error, a little window opens up at the bottom which shows you the part of the example where the error is.

In user testing, the fact that focus is being taken away from the content being validated to the results page was shown to be a problem: they'd like the focus to stay on the text and the errors to be just complementary to it, in order to have a fast validate-edit-validate feedback loop.

What's the best way to redesign the experience here to keep the focus on the text?

My initial thoughts are to split the window halfway so the errors are shown from the bottom, and the text itself never goes anywhere. Is there a better approach?