feat(Archive): Clayworth graph Sabidussi iso via G₂(2) generators

The Clayworth graph (4032 vertices, cubic, genus 505) is a Sabidussi
coset graph: Sab(G₂(2), C₃). Two generators (orders 7 and 6) of
G₂(2) ≤ Sym(4032) preserve adjacency, and BFS witness words prove
vertex-transitivity.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: RaggedR

Archive.lean

@@ -1,5 +1,6 @@
 import Archive.Arithcc
 import Archive.BolzaSurface
+import Archive.ClayworthSabidussi
 import Archive.ClayworthSurface
 import Archive.Examples.Eisenstein
 import Archive.Examples.IfNormalization.Result