Deliver ONE notification to a matched subscription's thread through the
topology. Returns the thread DO's Response (a 404 when the row's threadId is
not owned by its tenant — the fail-closed cross-tenant case). The whole
SendNotificationSignalInput is forwarded; the thread-DO /signal/notification
route reads what it needs (source/kind/summary/priority/payload/dedupeKey/
coalesceKey/attributes) and derives the resourceId from ITS own scope (a thread
has one owner — the row's resourceId — so delivery keys the inbox identically
whether the signal arrived from a client ingest or a provider webhook).
Deliver ONE notification to a matched subscription's thread through the topology. Returns the thread DO's Response (a 404 when the row's threadId is not owned by its tenant — the fail-closed cross-tenant case). The whole
SendNotificationSignalInputis forwarded; the thread-DO/signal/notificationroute reads what it needs (source/kind/summary/priority/payload/dedupeKey/ coalesceKey/attributes) and derives the resourceId from ITS own scope (a thread has one owner — the row's resourceId — so delivery keys the inbox identically whether the signal arrived from a client ingest or a provider webhook).