Before the deadly collapse of the Francis Scott Key Bridge in March that halted Port of Baltimore vessel traffic, the port had long topped the nation in automobile shipments. But after losing business in the nearly three months before the Patapsco River’s main shipping channel fully reopened, the port’s top ranking in autos and light trucks going forward isn’t as sure a bet. Though final numbers won’t be available until the end of December, shipments of autos and roll-on, roll-off machinery, which includes agricultural equipment, are down year-over-year.