If I copy a clean solution from stackoverflow, I put it into a separate file with the appropriate license header. IMO that's the absolute minimum degree of separation that any imported code, whether from StackOverflow or AI, should have.

Even if I then edit it to adapt and modify it, I'll just add my copyright header, but I can't replace/remove the original one.

That's a so invalid analogy, editors are effectively tools just like as a hammer because they require constant human input to produce something, the human is in constant control over the whole production process so they don't need to give attribution to the individual tools they used to build a house...

Unlike a black magic box where you just tell it to build something and it does all the production for you while you sit back.