The Seahawks’ downtown amphitheater, arguably the NFL’s loudest, has haunted the 49ers in past visits. A Super Bowl dream died here in the NFC Championship Game after the 2013 season. A 2004 shutout loss snapped the 49ers’ NFL-record scoring streak of 420 straight games. Sunday, the 49ers won their fourth straight game here, their best-ever stretch in this heated NFC West rivalry.