feat: Add in-memory implementations for issuer audit, key, repository, and trust management

- Introduced InMemoryIssuerAuditSink to retain audit entries for testing.
- Implemented InMemoryIssuerKeyRepository for deterministic key storage.
- Created InMemoryIssuerRepository to manage issuer records in memory.
- Added InMemoryIssuerTrustRepository for managing issuer trust overrides.
- Each repository utilizes concurrent collections for thread-safe operations.
- Enhanced deprecation tracking with a comprehensive YAML schema for API governance.

src/Scanner/__Tests/StellaOps.Scanner.Reachability.Tests/RichGraphPublisherTests.cs

@@ -1,4 +1,5 @@
 using System.Threading.Tasks;
+using StellaOps.Cryptography;
 using StellaOps.Scanner.Reachability;
 using Xunit;
 
@@ -9,7 +10,7 @@ public class RichGraphPublisherTests
     [Fact]
     public async Task PublishesGraphToCas()
     {
-        var writer = new RichGraphWriter();
+        var writer = new RichGraphWriter(CryptoHashFactory.CreateDefault());
         var publisher = new ReachabilityRichGraphPublisher(writer);
         var cas = new FakeFileContentAddressableStore();
 
@@ -21,7 +22,8 @@ public class RichGraphPublisherTests
         var rich = RichGraphBuilder.FromUnion(union, "test", "1.0.0");
         var result = await publisher.PublishAsync(rich, "scan-1", cas, temp.Path);
 
-        Assert.StartsWith("sha256:", result.GraphHash);
+        Assert.Contains(":", result.GraphHash); // hash format: algorithm:digest
+        Assert.StartsWith("cas://reachability/graphs/", result.CasUri);
         Assert.Equal(1, result.NodeCount);
     }
 }