Add signal contracts for reachability, exploitability, trust, and unknown symbols

- Introduced `ReachabilityState`, `RuntimeHit`, `ExploitabilitySignal`, `ReachabilitySignal`, `SignalEnvelope`, `SignalType`, `TrustSignal`, and `UnknownSymbolSignal` records to define various signal types and their properties.
- Implemented JSON serialization attributes for proper data interchange.
- Created project files for the new signal contracts library and corresponding test projects.
- Added deterministic test fixtures for micro-interaction testing.
- Included cryptographic keys for secure operations with cosign.

src/Policy/__Libraries/StellaOps.Policy.Storage.Postgres/ServiceCollectionExtensions.cs

@@ -37,6 +37,11 @@ public static class ServiceCollectionExtensions
         services.AddScoped<IReceiptRepository, PostgresReceiptRepository>();
         services.AddScoped<IExplanationRepository, ExplanationRepository>();
         services.AddScoped<IPolicyAuditRepository, PolicyAuditRepository>();
+        services.AddScoped<ISnapshotRepository, SnapshotRepository>();
+        services.AddScoped<IViolationEventRepository, ViolationEventRepository>();
+        services.AddScoped<IConflictRepository, ConflictRepository>();
+        services.AddScoped<ILedgerExportRepository, LedgerExportRepository>();
+        services.AddScoped<IWorkerResultRepository, WorkerResultRepository>();
 
         return services;
     }
@@ -64,6 +69,11 @@ public static class ServiceCollectionExtensions
         services.AddScoped<IReceiptRepository, PostgresReceiptRepository>();
         services.AddScoped<IExplanationRepository, ExplanationRepository>();
         services.AddScoped<IPolicyAuditRepository, PolicyAuditRepository>();
+        services.AddScoped<ISnapshotRepository, SnapshotRepository>();
+        services.AddScoped<IViolationEventRepository, ViolationEventRepository>();
+        services.AddScoped<IConflictRepository, ConflictRepository>();
+        services.AddScoped<ILedgerExportRepository, LedgerExportRepository>();
+        services.AddScoped<IWorkerResultRepository, WorkerResultRepository>();
 
         return services;
     }