As part of T100161: Convert all of MediaWiki core to OOUI PHP (tracking), agreed at the hackathon, mobile needs to stop using wgUseMediaWikiUIEverywhere, since it will be removed entirely.

That basically means testing with wgUseMediaWikiUIEverywhere false, then doing one of the following anywhere something doesn't look right:

• Convert to OO UI, either via FormSpecialPage or explicitly
• Manually pass in the mw-ui classes; this should be considered temporary since we want to move away from MW UI entirely (T100270: Replace use of jQuery UI and MW UI with OOUI across all Wikimedia-deployed extensions and core).