The default map view should be facade mode

[Wotuu]

Everyone who currently uses split_floors should be migrated to null, meaning 'default'. People can then still explicitly switch back to split_floors easily when #2528 is done. I mean they can still now, but it'd be much easier and prominent then.

This should probably prompt a full lightbox release to notify everyone that this has changed for them.

https://discord.com/channels/311861458847662081/1291543614090121359/1291867470381977811