Decouples the gw stream-read loop from the listener-fanout loop with a
bounded Channel<MxEvent> (default capacity 50_000) sitting between them.
When a slow listener fills the channel, the producer's TryWrite returns
false and we count the drop rather than back-pressuring the gw stream.
Three counters on the ZB.MOM.WW.OtOpcUa.Driver.Galaxy meter expose the
pressure curve before it manifests as user-visible loss:
- galaxy.events.received — MxEvents read from StreamEvents
- galaxy.events.dispatched — MxEvents that made it through to OnDataChange
- galaxy.events.dropped — MxEvents discarded because the channel was full
Each measurement carries a galaxy.client tag so multi-driver hosts can
split by source. The driver wires _options.MxAccess.ClientName into the
new EventPump constructor parameter.
Tests: drop-newest under pressure, capacity validation, and per-pump
measurement filtering (xUnit can run other pump tests in parallel and
their measurements land on the same listener — the test filters to its
own client name).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
