Make the whole top header fixed

agaric/templates/layout/page.html.twig

@@ -3,6 +3,7 @@
 {% block navbar %}
 {% if page.navbar_branding or page.navbar_social or page.primary_menu %}
 {# Top navbar #}
+<div class="is-fixed">
 <nav class="navbar" id="navbar">
   <div class="navbar-brand">
     {% if page.navbar_branding %}
@@ -30,5 +31,6 @@
     {% endif %}
   </div>
 </nav>
+</div>
 {% endif %}
 {% endblock navbar %}

agaric/templates/layout/region--primary-menu.html.twig

@@ -1,21 +0,0 @@
-{#
-/**
- * @file
- * Default theme implementation to display a region.
- *
- * Available variables:
- * - content: The content for this region, typically blocks.
- * - attributes: HTML attributes for the region <div>.
- * - region: The name of the region variable as defined in the theme's
- *   .info.yml file.
- *
- * @see template_preprocess_region()
- *
- * @ingroup themeable
- */
-#}
-{% if content %}
-  <div class="is-fixed">
-    {{ content }}
-  </div>
-{% endif %}