Each models.yaml entry now lists the locales its artifact recognizes, taken from the artifact itself, and a request picks the first entry that recognizes it, negotiated with LocaleService::NegotiateLanguages. That replaces the locale prefixes and the multilingual catch-all, so a language no model recognizes no longer reaches one that would transcribe it as another language. Differential Revision: https://phabricator.services.mozilla.com/D322688