Sitting in the Oval Office alongside senior Chinese officials this month, President Trump declared that the United States had reached “a substantial phase one deal” with China — a development that could ease an intensifying trade war that has roiled global markets and hurt many U.S. businesses and consumers.Nearly three years into his tenure, the president who promised to bring his “Art of the Deal” business savvy to foreign and trade policy has few substantive deals to his name — and he is running short on time to deliver big-ticket agreements ahead of Election Day next year.