feat(docker): ingest swarm topology + lifecycle events + health/restart alerts

Wires the agent's enriched + swarm payloads through the docker.persist_host_
samples capability:

  * Swarm topology — persist sample["swarm"] into docker_swarm_services /
    docker_swarm_nodes (upsert + prune stale, host-scoped so two managers don't
    clobber). Migration docker_005 adds services.placement_json for the
    task→node placement the agent now reports.
  * Lifecycle events — _derive_events (pure, unit-tested) diffs the newest
    snapshot against stored per-container state: start / stop / die (non-zero
    exit) / oom / health_change → docker_events rows. Skipped on a host's first
    snapshot so the baseline doesn't emit a start per existing container.
  * Alerts — record restart_count (always) and is_healthy (1.0/0.0, only when a
    HEALTHCHECK exists) alongside cpu/mem, under host-scoped resource names;
    METRIC_CATALOG[docker] gains restart_count + is_healthy so they're alertable.

host_agent ingest captures the newest sample's swarm object and threads it to
the capability (now persist_host_docker(session, host, snapshots, swarm=None));
invoked when containers OR swarm are present, under the same SAVEPOINT. Unit
tests cover the event-diff matrix; integration tests cover event derivation
across two snapshots and swarm topology round-trip (incl. placement).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016Jg27rgypiW2efULXJDtMC

plugins/docker/models.py

@@ -145,6 +145,10 @@ class DockerSwarmService(Base):
     desired: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
     running: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
     image: Mapped[str | None] = mapped_column(String(512), nullable=True)
+    # task→node placement of running replicas: [{"node_id", "running"}], JSON.
+    # A manager sees every task, so this captures cross-node placement that the
+    # local docker_containers rows (this host only) can't.
+    placement_json: Mapped[str] = mapped_column(Text, nullable=False, default="[]")
     updated_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False,
         default=lambda: datetime.now(timezone.utc),