The gateway's StreamEvents with after_worker_sequence = 0 is a fresh stream
and never replays, and the event pump started only on the first
Read/Subscribe, so platform ScanState probes advised before then lost their
initial value (and a driver with no authored tags never got any host status).
PerPlatformProbeWatcher now awaits an ensure-event-stream hook before every
probe SubscribeBulk (seed, discover sync, reconnect ResubscribeStaleAsync).
The driver's hook starts the pump (refused while a teardown is in progress)
and waits, bounded, on the new EventPump.StreamRequested signal - completed
once the stream loop's first MoveNext has issued the StreamEvents RPC, or
when the loop ends - so the advise never precedes the stream request.
Claude-Session: https://claude.ai/code/session_01GT67AD99zQQqpLCVm3p7xk
Joseph Doherty
e35f2a4e93