The end of the Fourth of July weekend arrived with a blast of troubling economic developments as bonds flashed signs of a coming recession and oil prices plunged, suggesting that millions of consumers who have spent more than a year rocked by rising prices could face even more upheaval. Tuesday’s events suggest that gasoline prices could be poised for a sharp descent, though there could be a multiweek lag. While the U.S. average has pulled back from its June peak above $5 a gallon, further declines might not be of much consolation to consumers because they could run into an economic downturn that further pressures stocks and could spill into the labor market.