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>

plugins/host_agent/templates/_host_vitals.html

@@ -5,6 +5,7 @@
    reports (the Agent panel below then shows provisioning). #}
 {% from "_macros.html" import status_badge, stat_tile %}
 {% macro pct(v) %}{{ '%.0f%%'|format(v) if v is not none else '—' }}{% endmacro %}
+{% set grades = grades or {} %}
 {% if reporting %}
 <section class="card host-health" aria-label="Host health">
   <div class="host-health-head">
@@ -22,10 +23,10 @@
     </span>
   </div>
   <div class="stat-strip host-health-tiles" style="margin-bottom:0;">
-    {{ stat_tile("CPU", pct(cpu), state=grades.cpu[0], hint=sparks.cpu|safe) }}
-    {{ stat_tile("Memory", pct(mem), state=grades.mem[0], hint=sparks.mem|safe) }}
-    {{ stat_tile("Disk /", pct(disk_root), state=grades.disk[0], hint=sparks.disk|safe) }}
-    {{ stat_tile("Load per core", pct(load_per_core), state=grades.load[0], hint=sparks.load|safe) }}
+    {{ stat_tile("CPU", pct(cpu), state=(grades.cpu or [status_class(cpu, 'cpu')])[0], hint=sparks.cpu|safe) }}
+    {{ stat_tile("Memory", pct(mem), state=(grades.mem or [status_class(mem, 'mem')])[0], hint=sparks.mem|safe) }}
+    {{ stat_tile("Disk /", pct(disk_root), state=(grades.disk or [status_class(disk_root, 'disk')])[0], hint=sparks.disk|safe) }}
+    {{ stat_tile("Load per core", pct(load_per_core), state=(grades.load or [status_class(load_per_core, 'load')])[0], hint=sparks.load|safe) }}
   </div>
   {% if usual and not stale %}
   <p class="field-hint" style="margin-top:0.6rem;">{{ usual | join("; ") | capitalize }}.</p>