WHEN VLADIMIR PUTIN’S tanks rolled into Ukraine in late February, crude-oil markets reacted instantly to the uncertainty and, in short order, to the sanctions imposed on Russia, the world’s second-biggest exporter of the black stuff. The war’s impact on another set of crucial oils—the edible vegetable fats such as sunflower oil, of which Ukraine and Russia are the world’s two biggest exporters—has taken longer to digest. It is now…