PHILADELPHIA - In the first big challenge to the proposed $26 billion national opioid settlement, the Philadelphia district attorney on Thursday sued Pennsylvania’s attorney general over the deal, saying the city stands to get only a pittance to cope with an epidemic that is killing more than 1,000 people a year.With Philadelphia pursuing its own, potentially more lucrative litigation against the opioid industry, District Attorney Larry Krasner denounced the national agreement and asked a state court to declare that Attorney General Josh Shapiro has no authority to bind the city to it.Krasner blasted Shapiro, a fellow Democrat, for acquiescing to a settlement that he said fails to hold opioid distributors and manufacturers sufficiently.