Apple's new CEO just pulled a $1,999 unreleased phone out of his tux pocket on the Emmys red carpet. Three seconds, and it answered the question that has stalked foldables for a decade. Can a tablet-size screen actually disappear into a pocket? The iPhone Duo unfolds into a 7.6 inch display, 50% larger than the Pro Max, and when open it's the thinnest iPhone ever made. Foldable makers have spent years running ads trying to prove their phones don't bulge. Ternus proved it in formalwear, the…