KIEV — Special counsel Robert Mueller’s team has been meeting over the last year with a Ukrainian lawmaker at the center of a controversial plan to end his country’s conflict with Russia, pressing him for details about interactions with Trump administration officials. Andrii Artemenko told POLITICO that FBI agents had peppered him with “assorted questions” over “at least” two interviews about his “meetings, dealings and the questions discussed with various levels of the American political establishment.” “These included congressmen, senators and representatives of the White House administration,” he added in a telephone conversation on Friday, after a meeting with members...