Adds an additive, site-wide, alarm-only gRPC stream backing the aggregated
Alarm Summary. Proto: new SiteStreamRequest { correlation_id } message + rpc
SubscribeSite(SiteStreamRequest) returns (stream SiteStreamEvent) on
SiteStreamService — purely additive, no field renumbering. Regenerated the
checked-in SiteStreamGrpc/*.cs.
Server: SubscribeInstance and the new SubscribeSite now delegate to a shared
RunSubscriptionStreamAsync helper (readiness/shutdown guards, correlation-id
validation, duplicate replacement, concurrency cap, bounded DropOldest channel,
relay actor, SiteConnectionOpened/Closed telemetry, guaranteed cleanup). The
only variation is the subscribe delegate: SubscribeSite calls
ISiteStreamSubscriber.SubscribeSiteAlarms (no per-instance filter). Added
SubscribeSiteAlarms to the ISiteStreamSubscriber contract (SiteStreamManager
already implements it from T1). StreamRelayActor reused unchanged — it already
drops IsConfiguredPlaceholder rows and maps the enriched AlarmStateUpdate.
Tests: SubscribeSite subscribes site alarms + removes on cancel, rejects unsafe
correlation ids, and relays a domain AlarmStateChanged as a proto
AlarmStateUpdate on the stream.
Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj
Joseph Doherty