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/social/_timeline_items.html

@@ -5,9 +5,9 @@
 {% if items %}
   {% set last = items[-1] %}
   {% if timeline_type == "actor" %}
-    <div hx-get="{{ url_for('ap_social.actor_timeline_page', id=actor_id, before=last.published.isoformat()) }}"
-         hx-trigger="revealed"
-         hx-swap="outerHTML">
+    <div sx-get="{{ url_for('ap_social.actor_timeline_page', id=actor_id, before=last.published.isoformat()) }}"
+         sx-trigger="revealed"
+         sx-swap="outerHTML">
     </div>
   {% endif %}
 {% endif %}