Ok, lets play the implication game. The states aceded to the Constitution unilaterally, so by implication, they can leave unilaterally.
Read Article I, Section 10, Clause 1 again.
Article I § 10 clause 1: 'Section 10 No State shall ... grant any Title of Nobility.' The election of a President is not a conferring of a title of nobility by a state.
Read Article I § 9 clause 8 again: 'No Title of Nobility shall be granted by the United States.'
Nonsense. They agreed to abide by the provisions of the Constitution when they were admitted to the Union. They were admitted by a vote of Congress.