feat(mcp): automation tools — playbooks, runs, schedules, alert actions, docker prune

MCP-6 #4970 "Automation tools: playbooks, runs, schedules, alert actions".

Viewer: list_playbooks, get_playbook (secret defaults masked), list_inventory
(variable names only), list_ansible_runs, get_ansible_run (log tail + grep),
list_schedules, wait_for_run (polls, 120s cap).

Operator: run_playbook (check mode unless check=false; a steward:confirm
playbook applies only with confirmed=true; secret variables reach the run
but are never stored, audited or returned), cancel_ansible_run, and
create/update/delete_schedule (secrets refused, check by default).

Admin: set_alert_action, and the docker plugin's prune_docker, which
previews from the disk report unless check=false (Ansible's check mode
skips the prune commands, so a check run would show nothing).

Every write is audited as "<user> via MCP" with the token id; the audit
tool's user filter includes those rows. prune_extra_vars moves to the
docker service so the page and the tool share it.

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

tests/plugins/docker/test_service.py

@@ -16,3 +16,14 @@ def test_bucket_keeps_short_series_and_averages_long_ones():
     out = svc.bucket([float(i) for i in range(400)], target=40)
     assert len(out) == 40
     assert out[0] == sum(range(10)) / 10
+
+
+def test_prune_extra_vars_mapping():
+    """The prune buttons drive one playbook via prune_target; only 'images'
+    widens to ALL unused images (docker image prune -a), system stays -f."""
+    assert svc.prune_extra_vars("containers") == {"prune_target": "containers"}
+    assert svc.prune_extra_vars("images") == {
+        "prune_target": "images", "prune_all_images": True,
+    }
+    # System prune stays conservative — no prune_all_images key.
+    assert svc.prune_extra_vars("system") == {"prune_target": "system"}