Welcome to FlyerTalk! Only later flights in the same reservation are cancelled due to no-show. So your "return" one way booking to PAE will stay as booked. If you book a new flight on Alaska to travel instead of your original, that too will stay intact.
Given there's no value of the ticket you're going to no-show for, I'd leave it as is (not tell Alaska you're cancelling) and hope that there is a cancellation or schedule change that allows you to keep some of the value, but otherwise, you're out the $ you paid for that.