If I was still in school I would write my docs in a Google Doc which provides the edit history. I could potentially also record video of me typing the entire document as well or screen recording my screen.
“After her work was flagged, Olmsted says she became obsessive about avoiding another accusation. She screen-recorded herself on her laptop doing writing assignments. She worked in Google Docs to track her changes and create a digital paper trail. She even tried to tweak her vocabulary and syntax. “I am very nervous that I would get this far and run into another AI accusation,” says Olmsted, who is on target to graduate in the spring. “I have so much to lose.”
That said, I'd imagine if someone resorts to using generative text their edits would contain anomalies that someone legitimately writing wouldn't have in terms of building out the structure/drafts. Perhaps that in itself could be auto detected more reliably.