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/playbook_editor.html

@@ -3,8 +3,8 @@
 {% from "_macros.html" import crumbs %}
 {% block title %}{{ "Edit" if editing else "New" }} Playbook — Steward{% endblock %}
 {% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Playbooks", "/ansible/playbooks"), (("Edit " ~ playbook_path) if editing else "New playbook", "")]) }}{% endblock %}
+{% block section_tabs %}{{ ansible_tabs("playbooks") }}{% endblock %}
 {% block content %}
-{{ ansible_tabs("playbooks") }}
 <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.25rem;gap:1rem;flex-wrap:wrap;">
   <h1 class="page-title" style="margin-bottom:0;">{{ "Edit playbook" if editing else "New playbook" }}</h1>
 </div>