docs: add CLAUDE.md redirecting to AGENTS.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: flemming-n-larsen

CLAUDE.md

@@ -1,3 +1 @@
-# Claude Instructions
-
-Read `AGENTS.md` at the start of every session — it is the routing hub for this project.
+@AGENTS.md