Supremacy Clause - the legislature’s duty under the US Constitution overrides state law.
Supremacy Clause does not apply.
The Constitution declares that a State may appoint Electors in what manner the State legislature may direct.
The Pennsylvania Assembly has directed through law and easily two centuries of practice that the manner is by popular election with the slate of Electors forwarded to Congress by the necessary date.
The election occurred. The process of certification and forwarding of Electors is occurring.
The Assembly has already acted in accordance to the Constitution on Presidential elections.
The question was on many mind as to whether they would choose to direct a different slate of Electors by direct appointment, which would be in their right. Competing slates have been submitted before for Congress to sort.
By the Constitution of the Commonwealth of Pennsylvania, their terms of office expired. They can not pass a resolution. Anything they may pass would and should be immediately challenged as contrary to their State Constitution.