LAS VEGAS — As the Raiders worked through a long, detailed, and meticulous coaching search that spanned 35 days and 15 candidates, a group of decision-makers that included minority owner Tom Brady and general manager John Spytek kept returning to a central theme. It’s what ultimately led them to Klint Kubiak , the Seahawks offensive coordinator, to be their next head coach. The Raiders officially introduced Kubiak as their new leader on Tuesday in Las Vegas, and in talking to people with