It’s a stunning box, a wizard object with a passel of amazing features (It’s a phone! An iPod! A Web browser!). But for all its marvels, the iPhone inaugurates a dangerous new era for Jobs. Has he peaked? Illustration by Default (Photo: Harald Franzen/Zuma Press) He saunters out onstage, and the first thing you think is, man, Steve Jobs looks old. The second thing you think is, no, not old: He finally looks his age. Well into his forties, Jobs appeared to have pulled off some kind of unholy Dorian Gray maneuver. But now, at 52, his hair is seriously...