<>The Constitution provides for no authority above that of a constitutional convention, so it is not clear that the courts — or any other institution — could intervene . . . <>
Thank God.
The authority is We the People, once again acting through our states. However, you are quite correct in that no other institution may intervene. Article V was purposely made a stand-alone section distinct from the others. It simply outlines peaceful means to improve government without resort to revolution.
But again - what stops them from derailing the Constitution as a whole, or redefining any of the Bill of Rights? Nothing.