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/ansible/index.html

@@ -5,8 +5,8 @@
 {% from "_macros.html" import page_header %}
 {% from "ansible/_tabs.html" import ansible_tabs %}
 {% block title %}Ansible Runs — Steward{% endblock %}
+{% block section_tabs %}{{ ansible_tabs("runs") }}{% endblock %}
 {% block content %}
-{{ ansible_tabs("runs") }}
 {% call page_header("Ansible Runs") %}
     <a href="/ansible/playbooks" class="btn">Run a playbook</a>
 {% endcall %}