Adds decnet.fleet.reconciler — a pure async function plus a long-lived
worker — that periodically reconciles the three sources of truth on a
DECNET host:
1. decnet-state.json (CLI-canonical fleet record)
2. fleet_deckies table (DB mirror, written by engine.deployer)
3. docker inspect (actual per-container runtime state)
Drift handling:
* JSON has X, DB doesn't → INSERT (deploy ran with DB offline)
* DB has X (this host), JSON doesn't → DELETE (teardown ran with DB offline)
* Both have X, docker disagrees → flip state to running/failed/degraded
* Docker socket unreachable → leave existing state alone (don't
torch every row to torn_down)
Cross-host safety: deletions are scoped to host_uuid for the local host;
a master that runs both a local fleet and swarm workers will never
clobber a peer's slice.
CLI:
decnet reconcile --once # one-shot, prints counts
decnet reconcile [--interval N] # long-lived worker, mirrors
# orchestrator's lifecycle (control
# listener + heartbeat + tick loop)
Promotes decnet/fleet.py → decnet/fleet/ package so the reconciler can
live alongside it without name collision (build_deckies_from_ini and
all_service_names re-exported unchanged via __init__.py).
14 new tests cover state aggregation rules, all four drift directions,
host_uuid scoping, docker-unreachable safety, and worker shutdown via
the bus control event.
