All nine service workers now participate in the host-local bus: sniffer,
prober, correlator (via profiler), profiler, collector, ingester, agent,
forwarder, updater. Pre-bus behavior is preserved end-to-end for
DECNET_BUS_ENABLED=false and get_bus() failures.
Three items intentionally deferred: realism-probe decky.{id}.state
(needs a realism probe path that doesn't exist yet), correlator session
boundaries (needs session state), and bus-wake subscriptions (publishes
landed; wake side wired to no subscriber today).