Placeholder AlarmStateChanged rows are a DebugView snapshot-only concept emitted
by InstanceActor.BuildAlarmStatesSnapshot; they are never a real alarm transition.
Their timestamp may be DateTimeOffset.MinValue (the Protobuf Timestamp lower boundary),
which can throw when packed via Timestamp.FromDateTimeOffset.
Added early-return guard at the top of HandleAlarmStateChanged before any timestamp
pack or channel write. Updated the existing NativeBindingLinkage round-trip test to
use a real (non-placeholder) native alarm; added DropsAlarmStateChanged_WhenIsConfiguredPlaceholder
to assert placeholders are silently dropped (15/15 pass).
Add two additive init-only fields to AlarmStateChanged so the Debug View can
nest live native conditions under their configured source-binding node:
- NativeSourceCanonicalName (binding canonical name, e.g. "Motor1.MotorAlarms")
- IsConfiguredPlaceholder (quiet-binding placeholder flag; default false)
Flow on BOTH cross-process paths:
- Live: proto AlarmStateUpdate fields 22/23 -> StreamRelayActor packs ->
SiteStreamGrpcClient unpacks (regenerated SiteStreamGrpc/Sitestream.cs).
- Snapshot (Newtonsoft): record defaults carry through; no special handling.
NativeAlarmActor.Emit now stamps NativeSourceCanonicalName = _source.CanonicalName.
Additive-only: no existing positional constructor or wire frame changed.
Tests: StreamRelayActorTests round-trips both fields pack->unpack;
NativeAlarmActorTests asserts the emitted event carries the binding canonical name.
Replace ValueFormatter.FormatDisplayValue with AttributeValueCodec.Encode
in StreamRelayActor so List<T> attribute values cross the gRPC wire as a
JSON array (e.g. ["a","b"]) rather than a comma-joined display string.
Scalars and null values are unaffected. Tests cover List→JSON, scalar
string pass-through, and null→empty-string.
Joseph Doherty