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/templates/docker/rows.html

@@ -54,8 +54,24 @@
           <div style="display:flex;align-items:center;gap:0.5rem;">
             <span class="dot {% if c.status == 'running' %}dot-up{% elif c.status == 'paused' %}dot-warn{% else %}dot-down{% endif %}"></span>
             <div>
-              <div style="font-weight:500;font-size:0.9rem;">{{ c.name }}</div>
-              <div style="font-size:0.73rem;color:var(--text-muted);">{{ c.status }}</div>
+              <div style="font-weight:500;font-size:0.9rem;">
+                {{ c.name }}
+                {% if c.health == 'healthy' %}<span title="healthy" style="color:var(--green);font-size:0.7rem;">●</span>
+                {% elif c.health == 'unhealthy' %}<span title="unhealthy" style="color:var(--red);font-size:0.7rem;">●</span>
+                {% elif c.health == 'starting' %}<span title="health: starting" style="color:var(--orange);font-size:0.7rem;">◐</span>{% endif %}
+              </div>
+              <div style="font-size:0.73rem;color:var(--text-muted);">
+                {{ c.status }}{% if item.uptime %} · up {{ item.uptime }}{% endif %}
+                {% if c.status != 'running' and c.exit_code is not none and c.exit_code != 0 %}
+                  · <span style="color:var(--red);">exit {{ c.exit_code }}{% if c.oom_killed %} (OOM){% endif %}</span>
+                {% endif %}
+                {% if c.restart_count %} · <span title="restart count" style="color:var(--orange);">⟳{{ c.restart_count }}</span>{% endif %}
+              </div>
+              {% if c.service_name or c.compose_project %}
+              <div style="font-size:0.68rem;color:var(--text-dim);margin-top:0.1rem;">
+                {{ c.service_name or c.compose_project }}
+              </div>
+              {% endif %}
             </div>
           </div>
         </td>