The Federal Reserve’s plan to raise interest rates this year, forged over months of strong jobs growth and a seemingly durable expansion, now faces an economy that no longer follows the script and may push the “liftoff” far into the future. The world’s largest economy slowed to a crawl in the first quarter and may actually have contracted. Lackluster retail sales and investment, sagging consumer confidence, a ballooning trade deficit and stagnant industrial output have all cast doubt over the central bank’s plans.