Fixed!
After triple checking all the external wiring, breaker, cords, etc., I was sure it was all correct, so took the top off the dryer to have a look inside, and volia! The neutral bonding jumper was disconnected, BUT, its loose metal ring connector was wedged against the dryer's frame. That's why I was getting a short between chassis ground and the white neutral lead (thus causing the breaker to instantly trip). Taped and zip-tied the literal loose end, and she starts and runs great. I think I'll name her Sparky.
