Rebrand sexp → sx across web platform (173 files)

Rename all sexp directories, files, identifiers, and references to sx.
artdag/ excluded (separate media processing DSL).

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

market/sx/headers.sx

@@ -0,0 +1,20 @@
+;; Market header components
+
+(defcomp ~market-shop-label (&key title top-slug sub-div)
+  (div :class "font-bold text-xl flex-shrink-0 flex gap-2 items-center"
+    (div (i :class "fa fa-shop") " " title)
+    (div :class "flex flex-col md:flex-row md:gap-2 text-xs"
+      (div top-slug) sub-div)))
+
+(defcomp ~market-sub-slug (&key sub)
+  (div sub))
+
+(defcomp ~market-product-label (&key title)
+  (<> (i :class "fa fa-shopping-bag" :aria-hidden "true") (div title)))
+
+(defcomp ~market-admin-link (&key href hx-select)
+  (a :href href :sx-get href :sx-target "#main-panel"
+     :sx-select hx-select :sx-swap "outerHTML" :sx-push-url "true"
+     :class "px-2 py-1 text-stone-500 hover:text-stone-700"
+     (i :class "fa fa-cog" :aria-hidden "true")))
+