Make positive input prompt drag resizable.

[FeepingCreature]

As per mention in Discord.

Problem: Drag bar currently occupies five invisible pixels at the bottom of the text widget. Not sure how to fix that in the layout.

[Acly]

It works pretty well.

Would be nice to have a visual indicator, and to avoid the extra layout space. You can put the widget on top of the text box by not adding it to the layout and using move to set a fixed position instead.

This is how the translation button is positioned, same code should work (could also consider moving it to the same place): https://github.com/Acly/krita-ai-diffusion/blob/main/ai_diffusion/ui/region.py#L393

As for visual indicator, something like this?

Diagonal lines in the bottom right are also typical, but the translation button is already there and moving it looks a bit weird: