Royal Opera House, LondonJohn Cranko's 1965 take on Pushkin's romance demands real artistry, and an outstanding cast delivers it A yellow moon peers out of a misty dawn sky. Two proud men and two distraught women gather for an encounter in which one man dies. With high jumps and stretched arabesques, arms shooting heavenwards, the women lever themselves over the men's bodies in a futile, fevered effort to stop a trag…