Nowhere in there does it say anything about the Overseer's office.
You aren't being banned, you weren't even on, and yes, the rules you agreed to made it very clear:
8. No unapproved expansions.
9. Obey the Overseer.
DISCLAIMER: Rules are subject to change! Always be sure to ask the Overseer for the current rules and guidelines.
With Lydia's Office signs saying to check in at the desk, not to mention
the locks on the door, I think its pretty obvious you weren't supposed to go into the Overseers office without authorization. By entering the office without authorization you broke Rule 9.
The secret room you made, which was also unauthorized, breaks Rule 8.
As for any new rules, I left them clearly visible outside of Lydia's office. There is also the disclaimer, that you agreed to, it isn't my fault you failed to follow them.