fix(ui): section tabs above the breadcrumb, so the Ansible tab strip holds still (#5214)

The tabs were drawn in each page's content block, which base.html renders
after the breadcrumb, so on every nested Ansible page the strip moved down a
line. base.html now has a section_tabs block above the breadcrumb, and every
Ansible page fills it. A guard in test_breadcrumbs.py fails any page that calls
a tabs macro outside that block.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/templates/base.html

@@ -153,6 +153,8 @@ document.addEventListener('keydown', function (e) {
         {% if error %}
         <div class="alert alert-error">{{ error }}</div>
         {% endif %}
+        {#- A section's tabs sit above its trail, so they hold still from page to page. #}
+        {% block section_tabs %}{% endblock %}
         {% block breadcrumb %}{% endblock %}
         {% block content %}{% endblock %}
     </main>