Refinery workers have reached a $15.5 million deal to resolve their class action against ConocoPhillips Co. that accused the company of failing to provide them with meal breaks during which they were relieved of all duties, the plaintiffs told a California federal court Monday.  The plaintiffs — the United Steelworkers Union and three workers — urged the court to grant preliminary approval to the deal, which comes after more than four years of litigation and covers wage and hour claims from refinery operators and lab workers.