Add CLAUDE.md alias to AGENTS.md

Summary:
And highlight the Internal/AGENTS.md file as well.  Without the change, Claude
tends to skip over the internal file because it treats it like content rather
than a directive.  Claude suggested the wording here.

Reviewed By: yoney

Differential Revision: D94697463

fbshipit-source-id: 6403489e0de2a6776b820df2d3aa484f675a2f64

Author: alexmalyshev

cinderx/AGENTS.md

@@ -3,9 +3,9 @@
 This file provides guidance to AI coding agents when working with code in this
 directory.
 
-If the file Internal/AGENTS.md exists, read this too. It contains details of
-things which are relevant to Meta's internal developer environment but do not
-apply for non Meta environments.
+**Important**: If the file `Internal/AGENTS.md` exists, you MUST read it before
+proceeding with any task. It contains additional context for internal
+development environments.
 
 ## Overview