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/_rule_fields.html

@@ -1,6 +1,7 @@
-{# alerts/_rule_fields.html — HTMX partial: resource + metric selects for a given source_module #}
+{# alerts/_rule_fields.html — the resource and metric pickers for one source;
+   the rule form includes it and swaps it in again when the source changes. #}
 <div class="form-group">
-  <label>Resource Name</label>
+  <label>Resource</label>
   {% if resources %}
   <select name="resource_name" required>
     {% if not current_resource %}<option value="" disabled selected>— pick a resource —</option>{% endif %}
@@ -10,20 +11,24 @@
   </select>
   {% else %}
   <select name="resource_name" required disabled>
-    <option value="">No data yet — run monitors first</option>
+    <option value="">Nothing has reported from this source yet</option>
   </select>
   <p class="field-hint">
-    Resource names populate from live metric data. Start the scheduler and try again.
+    The list fills from readings this source has recorded. Come back once it has reported.
   </p>
   {% endif %}
 </div>
 
 <div class="form-group">
-  <label>Metric Name</label>
-  <select name="metric_name" required>
+  <label>Metric</label>
+  <select name="metric_name" required data-metric-picker>
     {% if not current_metric %}<option value="" disabled selected>— pick a metric —</option>{% endif %}
     {% for m in metrics %}
-    <option value="{{ m }}" {% if m == current_metric %}selected{% endif %}>{{ m }}</option>
+    <option value="{{ m }}" data-unit="{{ metric_unit(m) }}" data-about="{{ metric_about(m) }}" {% if m in ("is_up", "is_healthy") %}data-binary{% endif %}
+            {% if m == current_metric %}selected{% endif %}>{{ metric_label(m) }}</option>
     {% endfor %}
   </select>
+  {% if current_metric and metric_about(current_metric) %}
+  <p class="field-hint" data-metric-about>{{ metric_about(current_metric) }}</p>
+  {% else %}<p class="field-hint" data-metric-about hidden></p>{% endif %}
 </div>