Audit the new local translation feature

Firefox 115 proposes automatic translations like Google Chrome, at least in Beta.

There's also an about:translations page.

Open questions:

• What are all the possible triggers for translation, which would expose the user's preferred language to the page? Are they all user-driven (no auto-translate)?
• Can we prevent websites from detecting the user's preferred language without an explicit activation by the user?
• Can we provide a less-fancy alternative that would not be exposed to websites? E.g. we just copy a safe subtree of the DOM and pass it into the translation machine and show the result in a non-interactive window, and don't touch the original page's DOM? Would this be that useful to users?
• Do we need to inform users that the use of the translation tool will be detectable by a web page?
• Are we able to trust the behaviour of the packaged AI provided my mozilla? Can we expose users to it?
• Do we need to audit the mozilla AI box? (Who's going to have to learn large language models, haha.)
• Is the translation potentially leaky to disk? Or is it all in-memory?