feat(docker): per-container enrichment — health, restarts, exit code, I/O, grouping

First slice of milestone 77 (Docker monitoring depth). Surfaces real per-container
stats beyond basic state, all read-only on the existing push model.

- agent (→1.4.0): collect_docker now inspects each container (health, restart
  count, exit code, OOM) and reads net + block I/O from the stats payload; pulls
  compose project + swarm service/task/node from container labels. Per-container
  inspect+stats calls run over a small bounded ThreadPool so the ~1s-per-stats
  blocking doesn't stretch the sample on a busy host.
- schema (docker_003): additive columns on docker_containers — health, exit_code,
  oom_killed, compose_project, service_name, task_id, node_id, and BigInteger
  net/blk byte counters.
- ingest: persists the enrichment + restart_count (.get keeps older agents working).
- ui: Docker page rows now show health badge, uptime ("up 3d 4h"), restart count,
  exit code (+OOM) for stopped containers, and compose/service grouping label.
- tests: agent helpers (grouping, inspect fields, net/IO sum) + collect_docker
  assembly incl. inspect; integration asserts enrichment round-trips.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016Jg27rgypiW2efULXJDtMC

plugins/docker/models.py

@@ -2,7 +2,9 @@
 from __future__ import annotations
 import uuid
 from datetime import datetime, timezone
-from sqlalchemy import DateTime, Float, ForeignKey, Index, Integer, String, Text
+from sqlalchemy import (
+    BigInteger, Boolean, DateTime, Float, ForeignKey, Index, Integer, String, Text,
+)
 from sqlalchemy.orm import Mapped, mapped_column
 from steward.models.base import Base
 
@@ -38,6 +40,23 @@ class DockerContainer(Base):
         default=lambda: datetime.now(timezone.utc),
     )
 
+    # ── Enrichment (agent ≥ 1.4.0) ────────────────────────────────────────────
+    # Health/exit/restart come from `docker inspect` (not the list endpoint);
+    # exit_code is only meaningful for stopped containers.
+    health: Mapped[str | None] = mapped_column(String(16), nullable=True)  # healthy|unhealthy|starting
+    exit_code: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    oom_killed: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    # Grouping: compose project + swarm placement, read off container labels.
+    compose_project: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    service_name: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    task_id: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    node_id: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    # Cumulative-since-start I/O counters (BigInteger — they exceed 2^31 quickly).
+    net_rx_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
+    net_tx_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
+    blk_read_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
+    blk_write_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
+
 
 class DockerMetric(Base):
     """Time-series CPU/memory per container — one row per sample per running