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/playbooks.html

@@ -7,8 +7,8 @@
 {% from "ansible/_tabs.html" import ansible_tabs %}
 {% block title %}Playbooks — Steward{% endblock %}
 {% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Playbooks", "")]) }}{% endblock %}
+{% block section_tabs %}{{ ansible_tabs("playbooks") }}{% endblock %}
 {% block content %}
-{{ ansible_tabs("playbooks") }}
 {% call page_header("Playbooks") %}
     {% if can_add %}<a href="/ansible/playbooks/new" class="btn">New playbook</a>{% endif %}
 {% endcall %}