NEW YORK — With less than three weeks until graduation at Columbia University, the markers of the annual celebration are everywhere. Students wearing light blue commencement gowns carry bundles of matching balloons. Nearby, other soon-to-be graduates exchange hugs and take selfies. Yet the rituals of the close of college life are happening in the shadow of a sprawling pro-Palestinian encampment at Columbia, where the arrests of more than 100 people on April 18 kicked off similar protests across the country. Just yards away from the smiling graduates, students sit on rugs and towels outside camping tents for day-long protests — making for…