So are a couple shells that use some kind of webkit tty. VS Code’s integrated terminal counts, I guess.
It could be an interesting paradigm, though, to have a hybrid between fullscreen and traditional tty programs: you output some forms, they are displayed by the terminal inline, but your scrollback just works like normal, and you can freely copy and paste stuff into the form. Once you submit the form, it becomes non-interactive, but stays in your scrollback buffer. You can select and copy textual data from it, but the form’s chrome cannot be selected as line drawing characters.
Probably could be a piece of concept art, I guess.
incidentally ttyphoon is a terminal that uses a browser base gui framework. maybe there is that browser for the teminal...