Uber and Rivian are joining forces to deploy 50,000 fully autonomous robotaxis over the next several decades, the companies announced Thursday. As part of the deal, Uber will invest $1.25 billion in Rivian through 2031, contingent on Rivian meeting certain autonomy milestones, starting with an initial $300 million at signing. (The deal is still subject to regulatory approval.)The news signals a big vote of confidence in Rivian’s nascent autonomy efforts, which include designing its own custom AI...