Major auto makers saw U.S. new-vehicle sales slip in the first half of 2019, which is expected to continue for the remainder of the year as the U.S. auto industry’s run of historic sales tapers off. Rising car prices and higher interest rates dulled demand in the year’s first six months, and many buyers flocked to the used-car lot looking for deals. A dramatic shift away from sedans and compact cars also dented sales volumes in the first part of the year as General Motors Co. and other auto makers discounted these models. …