fix(swarm): don't paint healthy deckies as failed when a shard-sibling fails

docker compose up is partial-success-friendly — a build failure on one
service doesn't roll back the others. But the master was catching the
agent's 500 and tagging every decky in the shard as 'failed' with the
same error message. From the UI that looked like all three deckies died
even though two were live on the worker.

On dispatch exception, probe the agent's /status to learn which deckies
actually have running containers, and upsert per-decky state accordingly.
Only fall back to marking the whole shard failed if the status probe
itself is unreachable.

Enhance agent.executor.status() to include a 'runtime' map keyed by
decky name with per-service container state, so the master has something
concrete to consult.

decnet/agent/executor.py

@@ -87,14 +87,44 @@ async def teardown(decky_id: str | None = None) -> None:
         await asyncio.to_thread(clear_state)
 
 
+def _decky_runtime_states(config: DecnetConfig) -> dict[str, dict[str, Any]]:
+    """Map decky_name → {"running": bool, "services": {svc: container_state}}.
+
+    Queried so the master can tell, after a partial-failure deploy, which
+    deckies actually came up instead of tainting the whole shard as failed.
+    Best-effort: a docker error returns an empty map, not an exception.
+    """
+    try:
+        import docker  # local import — agent-only path
+        client = docker.from_env()
+        live = {c.name: c.status for c in client.containers.list(all=True, ignore_removed=True)}
+    except Exception:  # pragma: no cover — defensive
+        log.exception("_decky_runtime_states: docker query failed")
+        return {}
+
+    out: dict[str, dict[str, Any]] = {}
+    for d in config.deckies:
+        svc_states = {
+            svc: live.get(f"{d.name}-{svc.replace('_', '-')}", "absent")
+            for svc in d.services
+        }
+        out[d.name] = {
+            "running": bool(svc_states) and all(s == "running" for s in svc_states.values()),
+            "services": svc_states,
+        }
+    return out
+
+
 async def status() -> dict[str, Any]:
     state = await asyncio.to_thread(load_state)
     if state is None:
         return {"deployed": False, "deckies": []}
     config, _compose_path = state
+    runtime = await asyncio.to_thread(_decky_runtime_states, config)
     return {
         "deployed": True,
         "mode": config.mode,
         "compose_path": str(_compose_path),
         "deckies": [d.model_dump() for d in config.deckies],
+        "runtime": runtime,
     }