It was the kind of news that shocks in the most abrupt way possible — crashing into the daily routine without warning, hovering for a while just beyond the reach of satisfactory explanation, then leaving behind a void that cannot be filled any time soon. Thus came the word of the passing yesterday of media provocateur Andrew Breitbart, reportedly while savoring one of the rare quiet moments in his tumultuous life, walking near his home in the Brentwood section of Los Angeles. He was 43, married and the father of four young children.