Add Specs section, Reflexive Web essay, fix highlight and dev caching

- Fix highlight() returning SxExpr so syntax-highlighted code renders
  as DOM elements instead of leaking SX source text into the page
- Add Specs section that reads and displays canonical SX spec files
  from shared/sx/ref/ with syntax highlighting
- Add "The Reflexive Web" essay on SX becoming a complete LISP with
  AI as native participant
- Change logo from (<x>) to (<sx>) everywhere
- Unify all backgrounds to bg-stone-100, center code blocks
- Skip component/style cookie cache in dev mode so .sx edits are
  visible immediately on refresh without clearing localStorage

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

sx/sxc/docs.sx

@@ -16,8 +16,8 @@
     children))
 
 (defcomp ~doc-code (&key code)
-  (div :class "bg-stone-50 border border-stone-200 rounded-lg p-4 overflow-x-auto"
-    (pre :class "text-sm" (code code))))
+  (div :class "bg-stone-100 rounded-lg p-5 mx-auto max-w-3xl"
+    (pre :class "text-sm leading-relaxed whitespace-pre-wrap break-words" (code code))))
 
 (defcomp ~doc-note (&key &rest children)
   (div :class "border-l-4 border-violet-400 bg-violet-50 p-4 text-stone-700 text-sm"
@@ -27,7 +27,7 @@
   (div :class "overflow-x-auto rounded border border-stone-200"
     (table :class "w-full text-left text-sm"
       (thead
-        (tr :class "border-b border-stone-200 bg-stone-50"
+        (tr :class "border-b border-stone-200 bg-stone-100"
           (map (fn (h) (th :class "px-3 py-2 font-medium text-stone-600" h)) headers)))
       (tbody
         (map (fn (row)