feat: Implement Runtime Facts ingestion service and NDJSON reader

- Added RuntimeFactsNdjsonReader for reading NDJSON formatted runtime facts.
- Introduced IRuntimeFactsIngestionService interface and its implementation.
- Enhanced Program.cs to register new services and endpoints for runtime facts.
- Updated CallgraphIngestionService to include CAS URI in stored artifacts.
- Created RuntimeFactsValidationException for validation errors during ingestion.
- Added tests for RuntimeFactsIngestionService and RuntimeFactsNdjsonReader.
- Implemented SignalsSealedModeMonitor for compliance checks in sealed mode.
- Updated project dependencies for testing utilities.

src/Scanner/__Libraries/StellaOps.Scanner.Storage/Catalog/ArtifactDocument.cs

@@ -12,6 +12,7 @@ public enum ArtifactDocumentType
     SurfaceManifest,
     SurfaceEntryTrace,
     SurfaceLayerFragment,
+    SurfaceObservation
 }
 
 public enum ArtifactDocumentFormat
@@ -25,6 +26,7 @@ public enum ArtifactDocumentFormat
     EntryTraceNdjson,
     EntryTraceGraphJson,
     ComponentFragmentJson,
+    ObservationJson
 }
 
 [BsonIgnoreExtraElements]