"During the existence of the Foundation" covers about 500 years in the series as written. The final book, chronologically, is Foundation and Earth (1986). In this novel,
Daneel is found living inside Earth's moon. He has been orchestrating his Plan A, which is the Gaia living planet that might eventually become Galaxia. He also had a Plan B, psychohistory. In the final sections of the book, he says "Over a period of years, the humaniform robots that have been working with me have been, one by one, called home. Their last tasks have been to remove all references to Earth in the planetary archives." Their withdrawal, to conserve Daneel's scarce resources, means that Gaia's development will be very slow.
It is not explicitly stated what the robots have been doing with respect to the Foundation itself. But it appears that they are not doing it any more, perhaps for a period of centuries. Their censorship efforts were certainly long ago enough to affect Pelorat's research, but probably not Lord Dorwin from the original Foundation, who seems to know about Alpha Centauri and Sol.
Consequently, I would guess that robots have mostly not been involved in the Foundation or Second Foundation, since they were either busy with other things, or deliberately kept home. But we do not have an explicit statement either way.