Columbia University’s interim president resigned from her position at the embattled Ivy League Friday night, just days after she told the Trump administration she would implement a mask ban — while privately promising faculty she would not. Katrina Armstrong’s decision to step down came in the wake of her high-profile battle with the Trump administration over the prestigious New York school’s $400 million in federal funding, sources told the Wall Street Journal Friday. Armstrong said she will return to her role as chief executive officer of the university’s Irving Medical Center, she told students and faculty in a letter Friday....