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.

etc/signals.yaml.sample

@@ -20,10 +20,16 @@ Signals:
     BypassNetworks:
       - "127.0.0.1/32"
       - "::1/128"
-  Mongo:
-    ConnectionString: "mongodb://localhost:27017/signals"
-    Database: "signals"
+  Mongo:
+    ConnectionString: "mongodb://localhost:27017/signals"
+    Database: "signals"
     CallgraphsCollection: "callgraphs"
     ReachabilityFactsCollection: "reachability_facts"
-  Storage:
-    RootPath: "../data/signals-artifacts"
+  Storage:
+    RootPath: "../data/signals-artifacts"
+  AirGap:
+    SealedMode:
+      EnforcementEnabled: false
+      EvidencePath: "../ops/devops/sealed-mode-ci/artifacts/sealed-mode-ci/latest/signals-sealed-ci.json"
+      MaxEvidenceAge: "06:00:00"
+      CacheLifetime: "00:01:00"