Cassidy Hutchinson, a onetime top aide to White House chief of staff Mark Meadows, testified that former President Donald Trump was warned that members of the crowd attending his rally on Jan. 6, 2021, were heavily armed and still directed them to march toward the Capitol. She also said she was told that Mr. Trump insisted on going to the Capitol with his supporters, even as officials, ultimately successfully, tried to stop him. Ms. Hutchinson recounted a dramatic altercation in the president’s limousine, known as “the beast,” after his Secret Service detail refused to drive him to the Capitol due...