feat(docker): Swarm task awareness — replaced tasks, service crash loops, last task error

Milestone 465 "Swarm task awareness". Fixes three defects from the live MCP
review #4973:
- #5008 "Swarm task history read as live state"
- #5009 "Crash-loop detection is blind to Swarm services"
- #5011 "Swarm task errors are not captured"

Agent and ingest (agent 1.8.0):
- A manager's agent now reports each service's newest tasks: slot, node,
  desired and current state, Swarm's Err/Message, exit code and time.
- They are stored in docker_swarm_services.tasks_json (migration
  docker_010_swarm_tasks).

Swarm view (pure):
- A task container is "replaced" when Swarm set its task's desired state off
  `running`. Without the task on record, a newer or running task in the same
  slot decides.
- Replaced containers are no longer replicas or crashes.
- Each service gets, from the task records:
  - failures_1h and failures_24h (failed or rejected tasks);
  - crash_looping (Settings → Thresholds count);
  - last_error, in Swarm's own words.

MCP:
- New findings: swarm_service_crash_looping (critical) and swarm_task_failed
  (warning, on a healthy service with a failure in 24h).
- Down and degraded findings name the last task error.
- list_swarm_services carries the failure fields.
- Container rows mark swarm_replaced and give a replaced task no problems.

Web:
- The containers page swarm cards and the Swarm topology page show crash
  loops, recent failures and the last task error.
- The dashboard widget flags a crash loop, and its "failed (24h)" count no
  longer counts a rolling update's killed task.

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

plugins/host_agent/agent.py

@@ -20,7 +20,7 @@ from collections import deque
 from concurrent.futures import ThreadPoolExecutor
 from datetime import datetime, timezone
 
-AGENT_VERSION = "1.7.0"
+AGENT_VERSION = "1.8.0"
 
 # Default path to the local Docker Engine socket. Overridable via the
 # `docker_socket` config key; collection is silently skipped if it's absent or
@@ -874,14 +874,46 @@ def _swarm_is_manager(info: dict) -> bool:
     return bool((info or {}).get("Swarm", {}).get("ControlAvailable"))
 
 
+# Newest tasks kept per service. Swarm retains about 5 per slot by default, so
+# this covers a replicated service's recent history and a crash loop's deaths
+# without shipping a global service's whole fleet every sample.
+SWARM_TASKS_PER_SERVICE = 10
+_TASK_TEXT_CHARS = 300
+
+
+def _swarm_task(t: dict) -> dict:
+    """One task as Steward stores it: where it ran, what Swarm wants of it,
+    what it is doing, and why it stopped (Err/Message, exit code)."""
+    status = t.get("Status") or {}
+    cstatus = status.get("ContainerStatus") or {}
+    exit_code = cstatus.get("ExitCode")
+    return {
+        "task_id": t.get("ID", "") or "",
+        "slot": t.get("Slot"),
+        "node_id": t.get("NodeID", "") or "",
+        "desired_state": (t.get("DesiredState") or "").lower(),
+        "state": (status.get("State") or "").lower(),
+        "message": (status.get("Message") or "")[:_TASK_TEXT_CHARS],
+        "error": (status.get("Err") or "")[:_TASK_TEXT_CHARS],
+        "exit_code": exit_code if isinstance(exit_code, int) else None,
+        "at": status.get("Timestamp") or t.get("UpdatedAt") or "",
+    }
+
+
 def _swarm_services(services: list, tasks: list) -> list:
     """Roll desired-vs-running replicas per service up from the task list.
 
     Replica health isn't on the service object — it's derived by counting tasks:
     `running` = tasks currently in state running; `desired` = the service's
     configured replica count (replicated) or the count of tasks the scheduler
-    wants running (global, which has no fixed number).
+    wants running (global, which has no fixed number). Each service also
+    carries its newest tasks (`tasks`), so Steward can tell a task Swarm
+    replaced from one that crashed, and say why the last one failed.
     """
+    tasks_by_svc: dict = {}
+    for t in (tasks or []):
+        if t.get("ServiceID"):
+            tasks_by_svc.setdefault(t["ServiceID"], []).append(_swarm_task(t))
     running_by_svc: dict = {}
     desired_by_svc: dict = {}  # only used for global-mode services
     placement: dict = {}       # svc_id -> {node_id: running_count}
@@ -921,6 +953,8 @@ def _swarm_services(services: list, tasks: list) -> list:
             # sees every task, even ones whose containers live on other hosts).
             "placement": [{"node_id": n, "running": cnt}
                           for n, cnt in sorted(placement.get(sid, {}).items())],
+            "tasks": sorted(tasks_by_svc.get(sid, []), key=lambda t: t["at"],
+                            reverse=True)[:SWARM_TASKS_PER_SERVICE],
         })
     return out