Will my auto insurance count me "at-fault" for being forced to collide with a railing?

yep, you are 100% at fault. The only way the other guy would have been at fault is if you actuall hit him and he was in your lane. Hitting the railing may have saved your life, but it is all on you. Since he didn't hit you there is no way this is going to be recorded as a hit and run. And they will not consider it no fault or everyone would claim "not my fault" for every accident.