Send all responses as sexp wire format with client-side rendering

- Server sends sexp source text, client (sexp.js) renders everything
- SexpExpr marker class for nested sexp composition in serialize()
- sexp_page() HTML shell with data-mount="body" for full page loads
- sexp_response() returns text/sexp for OOB/partial responses
- ~app-body layout component replaces ~app-layout (no raw!)
- ~rich-text is the only component using raw! (for CMS HTML content)
- Fragment endpoints return text/sexp, auto-wrapped in SexpExpr
- All _*_html() helpers converted to _*_sexp() returning sexp source
- Head auto-hoist: sexp.js moves meta/title/link/script[ld+json]
  from rendered body to document.head automatically
- Unknown components render warning box instead of crashing page
- Component kwargs preserve AST for lazy rendering (fixes <> in kwargs)
- Fix unterminated paren in events/sexp/tickets.sexpr

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

shared/browser/templates/oob_elements.html

@@ -4,7 +4,7 @@
 
 <div
   id="filter"
-  hx-swap-oob="outerHTML"
+  sx-swap-oob="outerHTML"
 >
 {% block filter %}
 {% endblock %}
@@ -14,14 +14,14 @@
 
 <aside
   id="aside"
-  hx-swap-oob="outerHTML"
+  sx-swap-oob="outerHTML"
   class="hidden md:flex md:flex-col max-w-xs md:h-full md:min-h-0 mr-3"
 >
 {% block aside %}
 {% endblock %}
 </aside>
 
-<div id="root-menu" hx-swap-oob="outerHTML" class="md:hidden">
+<div id="root-menu" sx-swap-oob="outerHTML" class="md:hidden">
   {% block mobile_menu %}
   {% endblock %}
 </div>