A state judge in Illinois ruled on Wednesday that former President Donald J. Trump had engaged in insurrection and was ineligible to appear on the state’s primary ballot. The decision creates uncertainty for the state’s March election, in which early voting is already underway.It also adds urgency for the U.S. Supreme Court to provide a national answer to the questions that have been raised about Mr. Trump’s eligibility to appear on ballots in more than 30 states.The judge, Tracie R. Porter of the State Circuit Court in Cook County, said the State Board of Elections had erred in…