feat(docker): per-host collection via the host agent; drop central scrape

Docker collection moves off the central single-socket scrape onto the host
agent, giving Docker a real per-host dimension. The Steward host now reports
its own containers like any other host, and same-named containers on different
hosts no longer collide.

- agent: stdlib UDS Docker client (AF_UNIX HTTP/1.1, Connection: close,
  chunked-aware), collect_docker() ports the cpu%/mem math; sample["docker"]
  added best-effort (silent-skip on absent/unreadable socket). AGENT_VERSION
  1.2.0 → 1.3.0; optional docker_socket config key.
- ingest: host_agent ingest hands per-host container snapshots to the docker
  plugin via a new "docker.persist_host_samples" capability (no hard import,
  no-op when docker disabled), inside a SAVEPOINT so a docker failure never
  sinks the host metrics. Resource names are host-scoped ("<host>/<name>").
- schema: docker_containers re-keyed (host_id, name); docker_metrics gains
  host_id; docker_002 migration DROP+recreates (dev-only, rule 122).
- ui: Docker page + widgets grouped by host with host links; new per-host
  Docker panel embedded on the Hosts hub (gated on docker enabled via a new
  enabled_plugins template context). Replaces the SQLite-only strftime
  bucketing with DB-agnostic Python bucketing.
- provisioning: install/provision playbooks add steward-agent to the docker
  group (best-effort) so the agent can read the socket.
- removed central scrape: docker scheduler.py + scraper.py deleted; plugin.yaml
  socket_path/scrape_interval_seconds/include_stopped dropped (plugin 2.0.0).
- tests: agent docker collector units (math, chunked decode, silent-skip,
  sample shape, config) + integration (host-scoped schema + persistence).

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

plugins/docker/templates/docker/host_panel.html

@@ -0,0 +1,22 @@
+{# docker/host_panel.html — per-host Docker fragment embedded on the Hosts hub #}
+<div class="card">
+  <div style="display:flex;align-items:baseline;justify-content:space-between;gap:0.6rem;margin-bottom:0.6rem;">
+    <h3 class="section-title" style="margin-bottom:0;">Docker</h3>
+    <span style="font-size:0.78rem;color:var(--text-muted);">
+      {{ running }} running{% if stopped %} · {{ stopped }} stopped{% endif %}
+      <a href="/plugins/docker/" style="margin-left:0.6rem;color:var(--text-muted);">All →</a>
+    </span>
+  </div>
+  <div style="display:grid;gap:2px;">
+    {% for c in containers %}
+    <div style="display:flex;align-items:center;gap:0.5rem;font-size:0.85rem;padding:0.2rem 0;">
+      <span class="dot {% if c.status == 'running' %}dot-up{% elif c.status == 'paused' %}dot-warn{% else %}dot-down{% endif %}"></span>
+      <span style="flex:1;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;" title="{{ c.image }}">{{ c.name }}</span>
+      <span style="font-size:0.74rem;color:var(--text-muted);font-family:ui-monospace,monospace;flex-shrink:0;">
+        {% if c.cpu_pct is not none %}{{ "%.1f" | format(c.cpu_pct) }}%{% endif %}
+        {% if c.mem_pct is not none %} · {{ "%.1f" | format(c.mem_pct) }}%{% endif %}
+      </span>
+    </div>
+    {% endfor %}
+  </div>
+</div>

plugins/docker/templates/docker/rows.html

@@ -1,4 +1,4 @@
-{# docker/rows.html — HTMX fragment for the Docker main page #}
+{# docker/rows.html — HTMX fragment for the Docker main page, grouped by host #}
 
 {# ── Summary strip ─────────────────────────────────────────────────────────── #}
 <div style="display:grid;grid-template-columns:repeat(auto-fill,minmax(140px,1fr));gap:0.75rem;margin-bottom:1.5rem;">
@@ -12,13 +12,28 @@
   </div>
   <div class="card" style="margin-bottom:0;">
     <div class="section-title" style="margin-bottom:0.35rem;">Total</div>
-    <span class="stat-val">{{ container_data | length }}</span>
+    <span class="stat-val">{{ total }}</span>
+  </div>
+  <div class="card" style="margin-bottom:0;">
+    <div class="section-title" style="margin-bottom:0.35rem;">Hosts</div>
+    <span class="stat-val">{{ host_groups | length }}</span>
   </div>
 </div>
 
-{# ── Container table ─────────────────────────────────────────────────────── #}
-{% if container_data %}
-<div class="card-flush">
+{# ── Container tables, one per host ───────────────────────────────────────── #}
+{% if host_groups %}
+{% for g in host_groups %}
+<div class="card-flush" style="margin-bottom:1.5rem;">
+  <div style="display:flex;align-items:baseline;gap:0.6rem;padding:0.5rem 0.75rem;border-bottom:1px solid var(--border);">
+    {% if g.host %}
+    <a href="/hosts/{{ g.host.id }}" style="font-weight:600;font-size:0.95rem;color:inherit;text-decoration:none;">{{ g.host.name }}</a>
+    {% else %}
+    <span style="font-weight:600;font-size:0.95rem;">{{ g.host_name }}</span>
+    {% endif %}
+    <span style="font-size:0.78rem;color:var(--text-muted);">
+      {{ g.running }} running{% if g.stopped %} · {{ g.stopped }} stopped{% endif %}
+    </span>
+  </div>
   <table class="table">
     <thead>
       <tr>
@@ -32,7 +47,7 @@
       </tr>
     </thead>
     <tbody>
-      {% for item in container_data %}
+      {% for item in g.containers %}
       {% set c = item.container %}
       <tr>
         <td>
@@ -77,10 +92,13 @@
     </tbody>
   </table>
 </div>
+{% endfor %}
 {% else %}
 <div class="card" style="text-align:center;padding:3rem;">
   <div style="color:var(--text-muted);font-size:0.9rem;">
-    No containers found. Make sure the Docker socket is accessible and the plugin is configured correctly.
+    No containers reported yet. Containers are collected by the Steward host agent —
+    deploy the agent to a host running Docker (Hosts → the host → agent panel) and
+    its containers will appear here under that host.
   </div>
 </div>
 {% endif %}

plugins/docker/templates/docker/widget.html

@@ -1,6 +1,6 @@
-{# docker/widget.html — dashboard widget: container status overview #}
-{% if not containers and running_count == 0 and stopped_count == 0 %}
-<p class="empty" style="padding:0.5rem 0;font-size:0.85rem;">No containers found.</p>
+{# docker/widget.html — dashboard widget: container status overview, by host #}
+{% if running_count == 0 and stopped_count == 0 %}
+<p class="empty" style="padding:0.5rem 0;font-size:0.85rem;">No containers reported yet.</p>
 {% else %}
 
 <div style="display:flex;gap:1rem;margin-bottom:0.65rem;">
@@ -16,8 +16,12 @@
   {% endif %}
 </div>
 
+{% for g in host_groups %}
+{% if multi_host %}
+<div style="font-size:0.72rem;color:var(--text-dim);text-transform:uppercase;letter-spacing:0.05em;margin:0.5rem 0 0.2rem;">{{ g.host_name }}</div>
+{% endif %}
 <div style="display:grid;gap:2px;">
-  {% for c in containers %}
+  {% for c in g.containers %}
   <div style="display:flex;align-items:center;gap:0.5rem;font-size:0.82rem;padding:0.15rem 0;">
     <span class="dot {% if c.status == 'running' %}dot-up{% elif c.status == 'paused' %}dot-warn{% else %}dot-down{% endif %}"></span>
     <span style="flex:1;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;">
@@ -31,5 +35,6 @@
   </div>
   {% endfor %}
 </div>
+{% endfor %}
 
 {% endif %}

plugins/docker/templates/docker/widget_resources.html

@@ -1,13 +1,14 @@
-{# docker/widget_resources.html — dashboard widget: CPU + memory bars for running containers #}
-{% if not containers %}
+{# docker/widget_resources.html — dashboard widget: CPU + memory bars, busiest containers #}
+{% if not rows %}
 <div style="color:var(--text-muted);font-size:0.85rem;padding:0.5rem 0;">No running containers.</div>
 {% else %}
 <div style="display:grid;gap:0.5rem;">
-  {% for c in containers %}
+  {% for r in rows %}
+  {% set c = r.c %}
   <div>
     <div style="display:flex;justify-content:space-between;align-items:baseline;margin-bottom:0.15rem;">
       <span style="font-size:0.8rem;font-weight:500;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;max-width:55%;">
-        {{ c.name }}
+        {{ c.name }}{% if multi_host %}<span style="color:var(--text-dim);font-weight:normal;"> · {{ r.host_name }}</span>{% endif %}
       </span>
       <span style="font-size:0.72rem;color:var(--text-muted);font-family:ui-monospace,monospace;flex-shrink:0;margin-left:0.5rem;">
         {% if c.cpu_pct is not none %}CPU {{ "%.1f" | format(c.cpu_pct) }}%{% endif %}