One common way of implementing the higher resolution image on click is to simply have the low resolution image as the embedded image but with a link to the higher resolution image. The other possibility is to use an incremental rendering or progressive format that will load and display at a lower resolution initially and then gain detail as it loads.
18+ months later and I think that Stylelint is probably the best path forward for those looking for a logical successor to Sass-linst.
Looking at my original list of requirements:
Supports sass and scss syntax - It supports these and more
Has a CLI that can integrate with CI workflows - It has a CLI
Has an easy JSON configuration syntax, and the tool will ...