feat(syslog): lines beside the readings: around an anomaly, in get_anomaly, and marked on host and SNMP charts (#6002)

get_anomaly's circumstances gain the host's or SNMP device's syslog
warnings and worse (mcp_events / mcp_resource_events). An anomaly row opens
"Syslog around it", read only when opened. A shared Chart.js plugin
(chart-marks.js) draws a dashed line at each syslog error on the host
metrics charts and an SNMP device's charts, with a line saying how many.

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

steward/mcp/tools/anomalies.py

@@ -161,7 +161,8 @@ async def get_anomaly(anomaly_id: str, occurrences: int = 5) -> dict:
       runs, other anomalies on the host, what plugins saw (container
       starts, deaths and OOM kills; maintenance jobs; reboots and agent
       stops; for a Traefik router, its swarm service's containers on any
-      host), and kind "steward": a stretch Steward itself wasn't recording
+      host; syslog warnings and worse from the host's or the SNMP device's
+      own log), and kind "steward": a stretch Steward itself wasn't recording
       (a restart or deploy), around which any reading can be wrong. From 30
       minutes before to 30 minutes after. Each kind keeps the 40 events
       nearest the occurrence's start; `around_left_out` counts the rest