feat(deployer): mirror fleet deploy/teardown into fleet_deckies table

CLI deploy now writes both surfaces: decnet-state.json (existing,
canonical for offline / no-API hosts) and the new fleet_deckies DB
table (visible to orchestrator, web dashboard, REST API).

Best-effort: a DB outage logs a warning and returns. The JSON file
remains the source of truth for `decnet status`, `decnet teardown`,
sniffer, and collector — operators on a CLI-only host keep working.

_run_async helper bridges sync deploy() into the async repository.
Always uses a fresh thread because the API handler at
web.router.fleet.api_deploy_deckies invokes deploy() from inside a
FastAPI event loop, which would otherwise break asyncio.run.

Verified end-to-end against MySQL: deploy mirror inserts rows, union
view (list_running_deckies) returns them with source="fleet",
teardown mirror removes them. Works from both sync (CLI) and async
(API handler) call sites.

decnet/engine/deployer.py

@@ -429,6 +429,83 @@ def _emit_lifecycle_event(
                     decky_name, trigger, exc)
 
 
+def _run_async(coro_factory) -> None:
+    """Run an async coroutine from a sync context, even when an event loop
+    is already running on this thread.
+
+    ``deploy()`` / ``teardown()`` are sync, but the API handler at
+    ``web.router.fleet.api_deploy_deckies`` calls them from inside its own
+    event loop.  ``asyncio.run`` refuses to run nested, so we always punt
+    to a fresh thread — small overhead, but deploy is already a heavy op.
+    """
+    import threading
+    err: list[BaseException] = []
+
+    def _runner() -> None:
+        try:
+            asyncio.run(coro_factory())
+        except BaseException as exc:  # noqa: BLE001
+            err.append(exc)
+
+    t = threading.Thread(target=_runner, daemon=False)
+    t.start()
+    t.join()
+    if err:
+        raise err[0]
+
+
+def _mirror_fleet_deploy_to_db(config: DecnetConfig) -> None:
+    """Mirror fleet rows into the ``fleet_deckies`` DB table.
+
+    Best-effort: a DB outage on a CLI-only host must not abort deploy.
+    The JSON state file (``decnet-state.json``) remains the canonical
+    artifact for every consumer that runs without the API daemon
+    (``decnet status``, ``decnet teardown``, sniffer, collector).
+
+    State defaults to ``running`` to mirror what the dashboard already
+    assumes about JSON-only fleet rows; the reconciler corrects drift
+    by polling ``docker inspect``.
+    """
+    try:
+        from decnet.web.db.factory import get_repository
+        from decnet.web.db.models import LOCAL_HOST_SENTINEL
+        repo = get_repository()
+
+        async def _go() -> None:
+            for d in config.deckies:
+                await repo.upsert_fleet_decky({
+                    "host_uuid": d.host_uuid or LOCAL_HOST_SENTINEL,
+                    "name": d.name,
+                    "services": list(d.services),
+                    "decky_config": d.model_dump(mode="json"),
+                    "decky_ip": d.ip,
+                    "state": "running",
+                })
+
+        _run_async(_go)
+    except Exception as exc:  # noqa: BLE001
+        log.warning("fleet DB mirror (deploy) failed (best-effort): %s", exc)
+
+
+def _mirror_fleet_teardown_to_db(deckies) -> None:
+    """Remove fleet rows from the DB.  Best-effort, same rationale."""
+    try:
+        from decnet.web.db.factory import get_repository
+        from decnet.web.db.models import LOCAL_HOST_SENTINEL
+        repo = get_repository()
+
+        async def _go() -> None:
+            for d in deckies:
+                await repo.delete_fleet_decky(
+                    host_uuid=d.host_uuid or LOCAL_HOST_SENTINEL,
+                    name=d.name,
+                )
+
+        _run_async(_go)
+    except Exception as exc:  # noqa: BLE001
+        log.warning("fleet DB mirror (teardown) failed (best-effort): %s", exc)
+
+
 @_traced("engine.deploy")
 def deploy(config: DecnetConfig, dry_run: bool = False, no_cache: bool = False, parallel: bool = False) -> None:
     log.info("deployment started n_deckies=%d interface=%s subnet=%s dry_run=%s", len(config.deckies), config.interface, config.subnet, dry_run)
@@ -476,6 +553,7 @@ def deploy(config: DecnetConfig, dry_run: bool = False, no_cache: bool = False,
         return
 
     save_state(config, compose_path)
+    _mirror_fleet_deploy_to_db(config)
 
     # Emit one creation event per decky so the correlation graph has a
     # well-formed lifecycle start (old_services=[] ⇒ new_services=<initial>).
@@ -546,6 +624,7 @@ def teardown(decky_id: str | None = None) -> None:
         )
         _compose("stop", *svc_names, compose_file=compose_path)
         _compose("rm", "-f", *svc_names, compose_file=compose_path)
+        _mirror_fleet_teardown_to_db([decky])
     else:
         for decky in config.deckies:
             _emit_lifecycle_event(
@@ -564,6 +643,7 @@ def teardown(decky_id: str | None = None) -> None:
             teardown_host_macvlan(decky_range)
         remove_macvlan_network(client)
         clear_state()
+        _mirror_fleet_teardown_to_db(config.deckies)
 
         net_driver = "IPvlan" if config.ipvlan else "MACVLAN"
         log.info("teardown complete all deckies removed network_driver=%s", net_driver)