Is there a repository for the hierarchy of proofs?
The Mizar system is a huge repository of math proofs. See the wikipedia page and the official website.


  of all of the known mathematical proofs that can be expressed using English statements


From wikipedia/Mizar_system#Mizar_language:


  The distinctive feature of the Mizar language is its readability


Proofs are written as articles, of which there are more than a thousand articles, and more than 50,000 proven theorems. The wikipedia page mentions some interesting ideas of the "QED manifesto", and how Mizar might be on its way to accomplishing this.


A huge graph of the Mizar library.

This paper might also be helpful: Combining Mizar and TPTP Semantic Presentation Tools