> If we could incrementally update our own brains by swapping cells for chips, what percentage of our brain has to be chips before us learning from a book is a violation of copyright?

The same percentage at which you stop qualifying to be human and become an unthinking tool, fully controlled by its operator to do whatever they want, without free will of its own and without any ethical concerns about abuse and slavery, like is the case with all LLMs.

(Of course, it is a moot point, because creating a human-level consciousness with chips is a thought experiment not grounded in reality.)

> When learning to recite a recent children's poem in kindergarten, what level of accuracy can a child attain before their ability to repeat it privately to one other person at a time is a copyright violation?

Any level thanks to the concept called human rights and freedoms, famously not applied to machines and other unthinking tools.