Tesla Inc. shares tanked more than 5% in the extended session Wednesday after the electric-vehicle maker teased a “next generation” electric-vehicle platform but stopped short of unveiling details. At the end of a four-hour investor day, Chief Executive Elon Musk sidestepped a question that sought details about the new vehicles’ performance and looks; the prototype timeline; and whether Tesla would start making them at an existing factory before moving production to its future Mexico factory, as it intends to do. “We…
