test(alerts): fix the silent-finding time and keep cpu_pct first in the host_agent catalog (#5062)

CI 8325: NOW - 10 min is 11:50, not 09:50; and rule_fields' refusal lists
the catalog in order, so seconds_since_seen goes last.

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

tests/mcp/test_tools.py

@@ -161,10 +161,10 @@ def test_alert_findings_say_when_a_metric_went_silent():
             no_data_since=silent), rule),
     ])
     assert (quiet["kind"], quiet["severity"]) == ("alert_no_data", "warning")
-    assert quiet["since"] == "2026-10-06T09:50:00Z" and "stopped reporting" in quiet["summary"]
+    assert quiet["since"] == "2026-10-06T11:50:00Z" and "stopped reporting" in quiet["summary"]
     # A firing alert that goes silent stays a firing finding, marked.
     assert (firing["kind"], firing["severity"]) == ("alert_firing", "critical")
-    assert "no data since 2026-10-06T09:50:00Z" in firing["summary"]
+    assert "no data since 2026-10-06T11:50:00Z" in firing["summary"]
 
 
 THRESHOLDS = {"cpu": {"warn": 80, "crit": 90}, "mem": {"warn": 80, "crit": 90},