test(alerts): seed metrics the way ingest does, through record_metrics (#5473)

#5473 "Opening an alert rule takes up to 15 s". With the rule pickers now
reading plugin_metric_latest, nine integration tests failed on rule_fields:
"host_agent has no resource 'box-…'". They seeded a resource by adding a raw
PluginMetric row, which no production path does: host-agent ingest and
record_metric both go through record_metrics, which keeps the latest-value
table. The seeds now go through record_metrics too.

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

tests/integration/test_renames.py

@@ -124,6 +124,7 @@ def test_a_renamed_host_carries_agent_and_container_metrics_and_their_rules(app)
     from sqlalchemy import select
     from steward.alerts import service as alert_svc
     from steward.models.alerts import AlertRule
+    from steward.core.alerts import record_metrics
     from steward.models.hosts import Host
     from steward.models.metrics import PluginMetric
 
@@ -140,8 +141,9 @@ def test_a_renamed_host_carries_agent_and_container_metrics_and_their_rules(app)
             async with s.begin():
                 s.add(Host(id=hid, name=old, address="10.8.8.8"))
                 s.add(Host(id=str(uuid.uuid4()), name=f"{old}x", address="10.8.8.9"))
-                for src, res in rows:
-                    s.add(PluginMetric(source_module=src, resource_name=res, metric_name="disk_used_pct", value=1))
+                await record_metrics(s, [PluginMetric(source_module=src, resource_name=res,
+                                                      metric_name="disk_used_pct", value=1)
+                                         for src, res in rows])
                 await s.flush()
                 fields = await alert_svc.rule_fields(
                     s, name=f"disk {tag}", source_module="host_agent", resource_name=f"{old}:/",