Fuck me, OP's a moron... the VM's "monitor" is set to 1024x768.
The output canvas has width="1024" height="768", but the CSS:
#screen_container canvas, #screen_container > div {
width: 100% !important;
height: 100% !important;
display: block;
}overwrites it, making everything be upscaled...
It would look fine upscaled if only no one added the CSS rule "image-rendering: pixelated"
Tried it removing the pixelated in the Dev tools. It looks like an old Win32 app running on 150% or 200% HiDPI scaled Windows with slightly blurry text. In any case much better than irregular pixelated scaling.
Sorry mate, a lot of this is vibe coded. Thanks for taking the time to check it out though