I think you’re overestimating how much data is available to a website.
I have to say, Qubes really sounds like what @hp185688 is looking for.
In order to read the hard drive, you need to do one of two things:
- open a file dialog and “upload” (either expose it to the local JS, or actually upload it to a server) a file to the website.
- give the script permission to access the filesystem, via a prompt. Similar to the one on this site that asks if you want to get desktop notifications.