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>

market/templates/macros/filters.html

@@ -19,11 +19,11 @@
 
   <a
     href="{{ href }}"
-    hx-get="{{ href }}"
-    hx-target="#main-panel"
-    hx-select="{{ hx_select_search }}"
-    hx-swap="outerHTML"
-    hx-push-url="true"
+    sx-get="{{ href }}"
+    sx-target="#main-panel"
+    sx-select="{{ hx_select_search }}"
+    sx-swap="outerHTML"
+    sx-push-url="true"
     role="button"
     aria-pressed="{{ 'true' if is_on else 'false' }}"
     title="{{ title }}"