docs(github): update PROVEN-INTEGRATION.md prover count to 128

Was missed in the previous CLAUDE.md sweep due to an Edit-without-Read
sequencing error. Cross-references the canonical PROVER_COUNT.md
tier table.

https://claude.ai/code/session_01YPqu7gti4azBach6ZvpRFJ

Author: claude

.github/PROVEN-INTEGRATION.md

@@ -12,7 +12,7 @@ This document outlines the recommended [proven](https://github.com/hyperpolymath
 
 ## Integration Notes
 
-ECHIDNA as a neurosymbolic theorem proving platform supporting 12 provers requires formally verified proof management:
+ECHIDNA as a neurosymbolic theorem proving platform supporting 128 prover backends (12 core; see [docs/PROVER_COUNT.md](../docs/PROVER_COUNT.md)) requires formally verified proof management:
 
 - **SafeGraph** models proof dependencies as DAGs. The `Acyclic` proof guarantees no circular dependencies in proof chains, and `topoSort` provides correct ordering for proof verification. `PathExists` verifies lemma reachability.