iPhone and iPad apps on a Mac

Fix:

• In an iPhone or iPad app running on a Mac ("Designed for iPhone/iPad"), Device.current now describes the Mac rather than the stand-in iPad the system reports (iPad8,6). It reads the model identifier from the hw.model sysctl, e.g. "Mac16,5" → "MacBook Pro (16-inch, 2024)", with family == .mac, and falls back to an unknown "Mac" if that doesn't name a Mac. Device.operatingSystemName is "macOS" there. The CPU brand string isn't readable from such an app, so chip is nil.

Documentation:

• The README and DocC explain why the data is bundled and never fetched.