I am confused about the Unbroken move for the Hero destiny playbook. It says, "You have Hope."
Does this mean the Hero playbook always rolls in Hope (aka rolling with Advantage)? Is there no limit to this?
Correct. Once you have that move, you always have Hope. The Hero never needs to work for it, they just have it.
Despair still cancels out this Hope, but otherwise yeah you always roll with Hope. And can never roll with Despair. It's a strong move.