Venezuelan opposition leader María Corina Machado is backing a long-term U.S. role in developing the country’s oil reserves, even as she questions who has the authority to sign the sweeping agreement announced by acting President Delcy Rodríguez. Machado said Thursday that the scope of the agreement remains unclear, including who is signing it, who will finance it, what guarantees investors would receive and how Venezuelans would benefit. Those are fairly consequential blanks for a deal covering some 65 billion barrels of Venezuelan…