SEATTLE — While discussing his quarterback situation in Seattle last month, Kalen DeBoer emphasized that “Austin Mack has been amazing this year. He’s been everything and then some, of what we hoped for and expected. The guy is going to play some big-time ball for us in this program. “He had just a great fall, got a lot of reps even in team sessions, wasn’t just hanging out on the scout team. He was with us, and you can just see what he’s capable of. So we’re super excited about him.” That’s increasingly clear. On Thursday, Mack — a redshirt freshman quarterback from Loomis, Calif. — announced…