It’s not in Article 1. The eligibility requirements for President are in Article 2, Section 1:
No person except a natural born citizen, or a citizen of the United States, at the time of the adoption of this Constitution, shall be eligible to the office of President; neither shall any person be eligible to that office who shall not have attained to the age of thirty five years, and been fourteen Years a resident within the United States.
The meaning of “natural born citizen” compared to citizen by birth or naturalized citizen was known to the Founders who drafted the Constitution. The meaning was clearly rooted in English Common Law. It was not defined in the Constitution because the States defined these terms based on English Common Law.
John Bingham, a Republican Congressman from the state of Ohio, stated in the House of Representatives in 1866 the unequivocal meaning of the phrase ‘Natural Born Citizen’
Every human being born within the jurisdiction of the United States of parents not owing allegiance to any foreign sovereignty is, in the language of your Constitution itself, a natural-born citizen; but, sir, I may be allowed to say further that I deny that the Congress of the United States ever had the power, or color of power to say that any man born within the jurisdiction of the United States, not owing a foreign allegiance, is not and shall not be a citizen of the United States. Citizenship is his birthright and neither the Congress nor the States can justly or lawfully take it from him.
Bingham was trained as a lawyer and would have been expert on English Common Law as this body of law was used to underpin the laws of the United States and is still used as historical reference material in the formulation of decisions.
Bingham’s statement “born within the jurisdiction of the United States of parents not owing allegiance to any foreign sovereignty” means born on the soil of the United States or its possessions, and of two citizen parents because dual citizenship was not allowed at the time. One could not be a citizen of the United States and at the same time a citizen of another country. A parent “owing allegiance to any foreign sovereignty” would not be a citizen of the United States.
Article 1 Section 8 (in part)
...To establish a uniform rule of naturalization,...
Those powers are enumerated to be with Congress. “Rule of naturalization” means Congress decides who is and who is not a natural born citizen.
Since you dodged the first question, let see if you can answer the second question. The first Congress dealt with the issue of natural born citizen as per enumeration in the Constitution. In the law that they passed, was a person required to be born on US soil to be a natural born citizen?
Oh, and English Common Law has no standing where the Constitution specifically defines the powers of the branches of government.