You could ship a terminal with your script. This is how apps like Slack deal with inconsistent handling of standardized content by shipping an embedded chromium.
The ChromeOS terminal (hterm[1]) is actually a pretty good terminal, so even a terminal might justify a browser context. Blink[2] on iOS for example uses it.
[1]: https://hterm.org/ (although in the way they do Google seems to have lost interest in updating that site and the GitHub repo, there's still fixes in the upstream Chromium repo)
