feat(mcp): understand and judge a metric anomaly: what happened, what was usual, what else went on (#5837)

get_anomaly gives each occurrence against what is usual at that hour, the
metric around the newest one with its normal, what else happened on the
resource's host around each occurrence (alert transitions, Ansible runs,
other anomalies there and a count elsewhere, plus plugins' own events
through a new mcp_events hook: the host agent's maintenance jobs and
downtime, Docker's container starts, deaths and OOM kills), and how earlier
anomalies on the same metric were judged.

get_metric_normal reads the learned slots and the level that would be
flagged. review_anomaly takes one id or several, all or nothing, with a
note. get_anomaly_settings and (admin) set_anomaly_settings read and change
the review window and each normal's floor, as Settings → Thresholds does.

metric_series.points takes an optional `until`; core.alerts gains
host_of_resource; floor_setting names its floor.

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

plugins/host_agent/__init__.py

@@ -62,6 +62,11 @@ async def mcp_overview(db) -> list[dict]:
     return await findings(db)
 
 
+async def mcp_events(db, host_id: str, host_name: str, since, until) -> list[dict]:
+    from .mcp_tools import mcp_events as events
+    return await events(db, host_id, host_name, since, until)
+
+
 def get_alert_metrics() -> dict[str, list[str]]:
     """Host metrics ingest records for alert rules (resource = the host name;
     disk_used_pct per mount, resource "<host>:<mount>"). seconds_since_seen