Per-site gRPC client for central-side streaming subscriptions to site
servers. SiteStreamGrpcClient manages server-streaming calls with
keepalive, converts proto events to domain types, and supports
cancellation via Unsubscribe. SiteStreamGrpcClientFactory caches one
client per site identifier.
Includes InternalsVisibleTo for test access to conversion helpers and
comprehensive unit tests for event mapping, quality/alarm-state
conversion, unsubscribe behavior, and factory caching.
Proto3 definition with SiteStreamService (server streaming), Quality and
AlarmStateEnum enums with UNSPECIFIED=0, google.protobuf.Timestamp for
cross-platform timestamps. Pre-generated C# stubs checked in (no protoc
at build time). 10 roundtrip tests covering serialization, oneof
discrimination, and Timestamp<->DateTimeOffset conversion.
Define the SiteStreamService proto for real-time instance event
streaming (attribute value changes, alarm state changes) from site
nodes to central. Add pre-generated C# stubs following the existing
LmxProxy pattern, gRPC NuGet packages with FrameworkReference for
ASP.NET Core server types, and proto roundtrip tests.
