feat(alerts): a covering rule's hosts fold away behind its "N hosts" (#5483)

#5483 "Alerts list: a covering rule's hosts start collapsed behind a toggle;
no dashed rows", from the operator's review of the Alerts list. Each rule is
its own tbody; its hosts sit in another, hidden until "N hosts" is pressed.
A rule with a host that isn't quiet opens on its own and names the host where
"last fired" was, so a problem never hides behind the fold. Host rows lose the
dashed rules for a sunken band under the indent.

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

steward/alerts/routes.py

@@ -139,6 +139,7 @@ async def list_alerts():
     # pressing of their states.
     rule_state = {r.id: alert_svc.alert_label(states[r.id]) for r in rules if r.id in states}
     children: dict[str, list] = {}
+    uneasy: dict[str, list[str]] = {}
     for r in rules:
         if r.parent_id:
             children.setdefault(r.parent_id, []).append(r)
@@ -149,11 +150,15 @@ async def list_alerts():
         rule_state[parent_id] = min(
             (lb for lb in labels if lb and lb not in ("inactive", "resolved")),
             key=lambda lb: alert_svc.ACTIVE_ORDER.get(lb, 9), default="inactive")
+        # The hosts that aren't quiet: named on the rule's row, and they keep
+        # its hosts open (#5483).
+        uneasy[parent_id] = [k.resource_name for k, lb in zip(kids, labels)
+                             if k.enabled and lb and lb not in ("inactive", "resolved")]
         fired[parent_id] = max((fired[k.id] for k in kids if k.id in fired), default=None)
     rules = sorted((r for r in rules if not r.parent_id),
                    key=lambda r: (not r.enabled, r.name.lower()))
     return await render_template(
-        "alerts/list.html", active=active, rules=rules, children=children,
+        "alerts/list.html", active=active, rules=rules, children=children, uneasy=uneasy,
         rule_state=rule_state, last_fired={k: v for k, v in fired.items() if v},
         notify=await _notify(), operators=_OPERATORS,
         poll_interval=current_app.config.get("MONITORS_POLL_INTERVAL", 60))