feat(ui): audit, alert rules and the rule form say things in words (#5212)

#5212 "Plain labels: no raw ids, scopes, metric keys or unexplained jargon",
batch 1:

- Audit log: each action reads as a sentence ("paused monitor"), with the
  code as its tooltip. Detail shows flags as yes/no, lists joined, a run's
  scope by name, spans as spans, and no ids the entity column already gives.
  The filter is now a picker of areas.
- Alert rules, history and Status say the condition in words: "is down",
  "Fullest disk >= 85%". Readings use metric_value, and history times use
  |ago.
- Rule form: sources and metrics by name, the threshold's unit, "fires
  when it is down/up" for an up/down metric instead of 0.5, and a metric
  reference built from the catalog.
- Schedules and Maintenance: viewers no longer see Run now, Pause, Edit,
  Delete or New. Intervals and next runs read as "every 2h" and "in 3h";
  a scope reads "Every alert on Host agent".

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

steward/templates/alerts/_history_page.html

@@ -3,12 +3,10 @@
 {% from "_macros.html" import status_badge, scroll_more, scroll_end %}
       {% for ev in events %}
       <tr>
-        <td style="font-family:ui-monospace,monospace;font-size:0.82rem;white-space:nowrap;">
-          {{ ev.at.strftime("%Y-%m-%d %H:%M:%S") }}
-        </td>
+        <td style="font-size:0.82rem;white-space:nowrap;">{{ ev.at|ago }}</td>
         <td>
           <a href="/alerts/history?rule={{ ev.rule.id }}&range={{ current_range }}">{{ ev.rule.name }}</a>
-          <div style="font-size:0.78rem;color:var(--text-dim);">{{ ev.rule.source_module }}/{{ ev.rule.resource_name }}</div>
+          <div style="font-size:0.78rem;color:var(--text-dim);">{{ source_label(ev.rule.source_module) }} · {{ ev.rule.resource_name }}</div>
         </td>
         <td style="white-space:nowrap;">
           {{ status_badge(ev.from_state) }}
@@ -18,9 +16,9 @@
           <div style="font-size:0.78rem;color:var(--text-muted);margin-top:0.25rem;white-space:normal;">{{ n }}</div>
           {% endfor %}
         </td>
-        <td style="font-family:ui-monospace,monospace;font-size:0.85rem;white-space:nowrap;">
-          {{ ev.rule.metric_name }} = {{ ev.value }}
-          <div style="font-size:0.75rem;color:var(--text-dim);">rule: {{ ev.condition }}</div>
+        <td style="font-size:0.85rem;white-space:nowrap;">
+          {{ ev.value }}
+          <div style="font-size:0.75rem;color:var(--text-dim);">fires when {{ ev.condition }}</div>
         </td>
         <td style="font-size:0.82rem;">
           {% if ev.muted_by %}