Walter H. Annenberg, the founder of TV Guide magazine who later served as ambassador to Great Britain, died today at his home in Wynnewood, Pa., of complications from pneumonia. He was 94. Annenberg, the son of publisher Moses Annenberg, inherited The Philadelphia Inquirer and two racing publications from his father and went on to build Triangle Publications, the first home of TV Guide magazine, into a multibillion-dollar business. He gave billions of dollars to charity and endowed the communication schools at the universities of Pennsylvania and Southern California.