Release v15.30.0

Summary

Adds append-aware observer completion waiting so clients can wait for observers after appends, receive complete failed-partition results, and use documented append workflows.

Added

• IAppendResultForObserverCompletion as a shared append-tail contract across append results, including event-store/namespace/sequence context and tail sequence number (#1845)
• WaitForCompletion client extension in Cratis.Chronicle.Observation returning AppendResultWaitForCompletionResult with completion status and failed partitions (#1845)
• IObservers.WaitForCompletion gRPC contract plus request/response messages for observer completion waits (#1845)
• Documentation for WaitForCompletion usage after both Append and AppendMany operations (#1845)
• Integration coverage for append/observer workflows with failing and concurrently processing observers to verify active observer processing behavior during failures (#1845)

Changed

• AppendResult and AppendManyResult now expose observer wait context through IAppendResultForObserverCompletion for direct use by the wait extension method (#1845)
• Append result handling now consistently reports operation tail sequence numbers for completion waits (SequenceNumber vs last SequenceNumbers item) (#1845)
• Observer-completion waiting now scopes failed-partition retrieval to affected observers to reduce unnecessary data reads (#1845)

Fixed

• Observer-completion waiting no longer exits on first failed partition; it now waits until affected observers are complete-or-failed and returns the complete failed-partition set for the operation (#1845)
• Append and append-many operations now succeed in testing scenarios where observer services are unavailable, preventing spec regressions introduced by observer wait wiring (#1845)

Removed

• None.

Security

• None.

Deprecated

• None.