A week into his job as Apple CEO, John Ternus handed the company's $1,999 folding iPhone to a streamer who barked at him, backflipped while holding it, and asked for one on the spot. Apple said yes. Ten days later, a box with two iPhone 18 Pro Maxes and a Watch Ultra showed up at his door. Run that sequence back and it reads as a campaign. The iPhone Duo is the most expensive iPhone Apple has ever sold, and pre-orders open October 16. That gives Apple five weeks to turn a folding phone into…