A Palo Alto man is charged with clubbing a teenage boy during an odd Portola Valley robbery attempt that ended with him plunging down a ravine in his SUV, a prosecutor said Thursday. Stefan Dombovic, 21, pleaded not guilty Wednesday in San Mateo County Superior Court to robbery, assault and burglary charges stemming from the Sunday night confrontation, District Attorney Steve Wagstaffe said. The trouble started when a 13-year-old boy who heard a vehicle pull into his Portola Valley driveway at around 10:10 p.m. Without waking his parents, he went to investigate. The boy spotted a man rummaging through his...