Upgrade development dependency to Xcode 26

[Abizern]

It's the current version available on the App Store. Eventually it's going to be a requirement for AppStore builds so we might as well make the move now. There may be some issues with the new concurrency model, but there will be other tasks to clean them up.

[nickoneill]

I haven't taken a look at this at all, but I would guess there are some design considerations to look at when we move to Xcode 26 as well? Worth keeping this up to date though.

[Abizern]

I don’t think it will change the look already applied on new devices. By moving up it will be easier to fix anything that may look off.