A galvanic cell is assembled using the half-cells Cu(s) | Cu^{2+}(aq, 1.0 M) and Ag(s) | Ag^{+}(aq, 1.0 M). The compartments are connected by a KNO_{3}(aq) salt bridge. While the cell operates spontaneously, which ion from the salt bridge migrates into the cathode compartment?