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>

account/templates/_types/auth/_newsletter_toggle.html

@@ -1,9 +1,9 @@
 <div id="nl-{{ un.newsletter_id }}" class="flex items-center">
   <button
-    hx-post="{{ account_url('/newsletter/' ~ un.newsletter_id ~ '/toggle/') }}"
-    hx-headers='{"X-CSRFToken": "{{ csrf_token() }}"}'
-    hx-target="#nl-{{ un.newsletter_id }}"
-    hx-swap="outerHTML"
+    sx-post="{{ account_url('/newsletter/' ~ un.newsletter_id ~ '/toggle/') }}"
+    sx-headers='{"X-CSRFToken": "{{ csrf_token() }}"}'
+    sx-target="#nl-{{ un.newsletter_id }}"
+    sx-swap="outerHTML"
     class="relative inline-flex h-6 w-11 items-center rounded-full transition-colors focus:outline-none focus:ring-2 focus:ring-emerald-500 focus:ring-offset-2
       {% if un.subscribed %}bg-emerald-500{% else %}bg-stone-300{% endif %}"
     role="switch"

account/templates/_types/auth/_newsletters_panel.html

@@ -22,10 +22,10 @@
                 {# No subscription row yet — show an off toggle that will create one #}
                 <div id="nl-{{ item.newsletter.id }}" class="flex items-center">
                   <button
-                    hx-post="{{ account_url('/newsletter/' ~ item.newsletter.id ~ '/toggle/') }}"
-                    hx-headers='{"X-CSRFToken": "{{ csrf_token() }}"}'
-                    hx-target="#nl-{{ item.newsletter.id }}"
-                    hx-swap="outerHTML"
+                    sx-post="{{ account_url('/newsletter/' ~ item.newsletter.id ~ '/toggle/') }}"
+                    sx-headers='{"X-CSRFToken": "{{ csrf_token() }}"}'
+                    sx-target="#nl-{{ item.newsletter.id }}"
+                    sx-swap="outerHTML"
                     class="relative inline-flex h-6 w-11 items-center rounded-full transition-colors focus:outline-none focus:ring-2 focus:ring-emerald-500 focus:ring-offset-2 bg-stone-300"
                     role="switch"
                     aria-checked="false"