Add unit tests for PackRunAttestation and SealedInstallEnforcer

- Implement comprehensive tests for PackRunAttestationService, covering attestation generation, verification, and event emission.
- Add tests for SealedInstallEnforcer to validate sealed install requirements and enforcement logic.
- Introduce a MonacoLoaderService stub for testing purposes to prevent Monaco workers/styles from loading during Karma runs.

src/Policy/StellaOps.Policy.Registry/StellaOps.Policy.Registry.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <LangVersion>preview</LangVersion>
+    <RootNamespace>StellaOps.Policy.Registry</RootNamespace>
+    <AssemblyName>StellaOps.Policy.Registry</AssemblyName>
+    <Description>Policy Registry typed clients and contracts for StellaOps Policy Engine</Description>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Http" Version="9.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Options" Version="9.0.0" />
+  </ItemGroup>
+
+</Project>