fix(mcp): get_anomaly keeps the events nearest the occurrence and says how many it left out (#5861)

Each source in an anomaly's `around` was cut to its oldest 40 with
nothing in the reply to say so; on a busy host the events nearest the
occurrence were the ones dropped. Each source now keeps the 40 nearest
the occurrence's start, and `around_left_out` counts the rest. Sources
return everything their bounded query read (Docker and the host agent
no longer cut at 40 and 20 themselves), so the count is honest.

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

plugins/docker/mcp_tools.py

@@ -758,7 +758,7 @@ async def mcp_events(db, host_id: str, host_name: str, since, until) -> list[dic
     from steward.mcp.tools._events import event
     rows = (await db.execute(select(DockerEvent).where(
         DockerEvent.host_id == host_id, DockerEvent.at >= since, DockerEvent.at <= until)
-        .order_by(DockerEvent.at).limit(40))).scalars()
+        .order_by(DockerEvent.at).limit(500))).scalars()
     return [event(e.at, "container", f"{e.container_name} {e.event}" + (f" ({e.detail})" if e.detail else ""),
                   subject=f"{host_name}/{e.container_name}") for e in rows]