The painted wooden sign resting on the base of the podium in Ocean Park read Savor the Moment, and when celebrated poet Sonia Sanchez stepped to the microphone to begin her program during Della Hardman Day on Saturday, it was impossible to imagine doing anything else. Words on a page are poor conveyors of the rhythms and intonations of Mrs. Sanchez’s commanding voice, which has been holding audiences rapt for decades.