After writer Salman Rushdie was stabbed onstage at the Chautauqua Institution on Friday, the idyllic New York community of Chautauqua, known for its annual summer educational and cultural programs and tranquil lakeside setting, was thrust into the international spotlight. For those on the ground, Friday’s events punctured the image of a utopian summer retreat — typically marked by thought-provoking panel discussions and leisurely swims. Sam Peters, 19, who has been attending Chautauqua Institution events with his grandfather since he was a baby, said the mood after the attack was one of disbelief, with many Chautauqua regulars asking, “How could this happen here?”