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>

relations/bp/fragments/routes.py

@@ -25,22 +25,14 @@ def register():
     async def get_fragment(fragment_type: str):
         handler = _handlers.get(fragment_type)
         if handler is None:
-            return Response("", status=200, content_type="text/html")
-        html = await handler()
-        return Response(html, status=200, content_type="text/html")
+            return Response("", status=200, content_type="text/sexp")
+        src = await handler()
+        return Response(src, status=200, content_type="text/sexp")
 
     # --- generic container-nav fragment ----------------------------------------
 
     async def _container_nav_handler():
-        """Render nav items for all visible relations of a container entity.
-
-        Query params:
-            container_type: entity type (e.g. "page")
-            container_id:   entity id
-            post_slug:      used for URL construction
-            exclude:        comma-separated relation types to skip
-        """
-        from shared.sexp.jinja_bridge import sexp as render_sexp
+        from shared.sexp.helpers import sexp_call
         from shared.sexp.relations import relations_from
         from shared.services.relationships import get_children
         from shared.infrastructure.urls import events_url, market_url
@@ -84,18 +76,16 @@ def register():
                     path = f"/{slug}/"
                 url_fn = _SERVICE_URL.get(defn.to_type)
                 href = url_fn(path) if url_fn else path
-                parts.append(render_sexp(
-                    '(~relation-nav :href href :name name :icon icon :nav-class nav-class :relation-type relation-type)',
+                parts.append(sexp_call("relation-nav",
                     href=href,
                     name=child.label or "",
                     icon=defn.nav_icon or "",
-                    **{
-                        "nav-class": nav_class,
-                        "relation-type": defn.name,
-                    },
-                ))
+                    nav_class=nav_class,
+                    relation_type=defn.name))
 
-        return "\n".join(parts)
+        if not parts:
+            return ""
+        return "(<> " + " ".join(parts) + ")"
 
     _handlers["container-nav"] = _container_nav_handler