fix(norms): templates grade by the cutoffs when handed no grade; the parts test reads inside transactions (#5742)

CI 9128: the host vitals and monitor templates required the new grades, so
callers (and tests) that render them without one failed; they now fall back
to status_class. The new integration test read outside begin(), which
autobegan the session.

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

steward/templates/monitors/rows.html

@@ -51,7 +51,7 @@
     {% if d.state in ('down', 'paused', 'pending') %}{{ status_badge(d.state) }}
     {% elif latest.response_ms is not none %}
       {% if d.spark %}<span class="mon-spark" title="Response time over the last 30 checks">{{ d.spark|safe }}</span>{% endif %}
-      <span class="tone-{{ d.latency }}"{% if d.latency_usual %} title="{{ d.latency_usual|capitalize }}"{% endif %}>{{ "%.0f"|format(latest.response_ms) }} ms</span>
+      <span class="tone-{{ d.latency or status_class(latest.response_ms, 'latency') }}"{% if d.latency_usual %} title="{{ d.latency_usual|capitalize }}"{% endif %}>{{ "%.0f"|format(latest.response_ms) }} ms</span>
     {% elif m.type == 'dns' and latest.resolved_ip %}<span class="tone-ok">{{ latest.resolved_ip }}</span>
     {% else %}{{ status_badge('up') }}{% endif %}
   </div>