During an especially strong Salzburg Festival this summer, including a poignant “Alcina” with Cecilia Bartoli, this was unforgettable: George Enescu’s rarely performed Oedipus opera, a perfect match for the director Achim Freyer’s surreal, symbol-laden, carefully childlike style. The stage was covered in his signature faux-naïve chalk drawings — and puppets, giant rag dolls, primary colors, skull masks, the juxtaposition of elongated and squat figures, expressionistically bold makeup and glacial movement. They all conjured a fairy-tale nightmare, while Ingo Metzmacher expertly unleashed the Vienna Philharmonic’s full radiance.