Phase 5: Page layouts as s-expressions — components, fragments, error pages

Add 9 new shared s-expression components (cart-mini, auth-menu,
account-nav-item, calendar-entry-nav, calendar-link-nav, market-link-nav,
post-card, base-shell, error-page) and wire them into all fragment route
handlers. 404/403 error pages now render entirely via s-expressions as a
full-page proof-of-concept, with Jinja fallback on failure.

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

market/bp/fragments/routes.py

@@ -33,6 +33,10 @@ def register():
     # --- container-nav fragment: market links --------------------------------
 
     async def _container_nav_handler():
+        from quart import current_app
+        from shared.infrastructure.urls import market_url
+        from shared.sexp.jinja_bridge import sexp as render_sexp
+
         container_type = request.args.get("container_type", "page")
         container_id = int(request.args.get("container_id", 0))
         post_slug = request.args.get("post_slug", "")
@@ -42,10 +46,16 @@ def register():
         )
         if not markets:
             return ""
-        return await render_template(
-            "fragments/container_nav_markets.html",
-            markets=markets, post_slug=post_slug,
-        )
+        styles = current_app.jinja_env.globals.get("styles", {})
+        nav_class = styles.get("nav_button_less_pad", "")
+        parts = []
+        for m in markets:
+            href = market_url(f"/{post_slug}/{m.slug}/")
+            parts.append(render_sexp(
+                '(~market-link-nav :href href :name name :nav-class nav-class)',
+                href=href, name=m.name, **{"nav-class": nav_class},
+            ))
+        return "\n".join(parts)
 
     _handlers["container-nav"] = _container_nav_handler