Tumbling sales of Fiat Chrysler’s main midsize car have driven the company to indefinitely lay off 1,300 employees at a Detroit-area factory. Workers on the second shift at Fiat Chrysler’s assembly plant in Sterling Heights, Michigan, will be furloughed starting July 5 as the slow-selling Chrysler 200 has started to stack up on dealer lots. Sales of the cars were down 61 percent through March, and inventory grew to a 150-day supply, according to Ward’s Automotive. Automakers consider 60 days to be optimal to give dealers enough of a selection for customers. Fiat Chrysler sold only 7,500 of the cars...