Add render stepper to home page

Replace header source view with interactive CEK render stepper.
Auto-parses on mount, step forward/back through DOM construction
with CSSX styling. Uses lake for preview persistence.

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

sx/sx/docs-content.sx

@@ -2,7 +2,7 @@
 
 (defcomp ~docs-content/home-content ()
   (div :id "main-content" :class "max-w-3xl mx-auto px-4 py-6"
-    (~docs/code :code (highlight (component-source "~layouts/header") "lisp"))))
+    (~home/stepper)))
 
 (defcomp ~docs-content/docs-introduction-content ()
   (~docs/page :title "Introduction"