Brian Steinberg Senior TV Editor Madison Avenue pulled hundreds of millions of dollars out of primetime TV and sent them to streaming venues in the industry’s recently completed “upfront” market, the latest sign that one of the media sector’s most stable mediums is in an era of severe flux. Ad commitments for primetime broadcast TV fell 3%, to $9.595 billion, compared with $9.91 billion in last year’s market, according to Media Dynamics Inc., an advertising consultancy that tracks the upfront, when U.S. TV networks try to sell the bulk of their commercial inventory for their next programming cycle.