[Feature Request] See underlying image when editing mask as separate layer

[Vargock]

Currently, when editing a mask that is a separate layer, the image is replaced with a black-and-white mask editor. This makes it very hard to accurately trace or refine details, because you can't see the underlying image to know exactly what you're masking.

Feature Suggestion:

It would be extremely helpful to be able to see the image beneath while painting the mask — maybe as a semi-transparent overlay or in split view. This would allow for much more precise and intuitive mask editing without needing to commit changes and constantly switch back to preview.

Why would it help:

When adding and editing a mask layer, the current workflow involves a lot of trial-and-error — you have to paint blindly, commit, preview, then go back and adjust. Being able to see the image while editing the mask would make the process much faster and more intuitive.

Thanks for the awesome work on the module!