Add tests for SBOM generation determinism across multiple formats

- Created `StellaOps.TestKit.Tests` project for unit tests related to determinism.
- Implemented `DeterminismManifestTests` to validate deterministic output for canonical bytes and strings, file read/write operations, and error handling for invalid schema versions.
- Added `SbomDeterminismTests` to ensure identical inputs produce consistent SBOMs across SPDX 3.0.1 and CycloneDX 1.6/1.7 formats, including parallel execution tests.
- Updated project references in `StellaOps.Integration.Determinism` to include the new determinism testing library.

tests/integration/StellaOps.Integration.Determinism/StellaOps.Integration.Determinism.csproj

@@ -29,17 +29,19 @@
   <ItemGroup>
     <!-- Policy scoring for determinism tests -->
     <ProjectReference Include="../../../src/Policy/__Libraries/StellaOps.Policy.Scoring/StellaOps.Policy.Scoring.csproj" />
-    
+
     <!-- Proof chain for hash verification -->
     <ProjectReference Include="../../../src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/StellaOps.Attestor.ProofChain.csproj" />
-    
+
     <!-- Cryptography for hashing -->
     <ProjectReference Include="../../../src/__Libraries/StellaOps.Cryptography/StellaOps.Cryptography.csproj" />
-    
+
     <!-- Canonical JSON -->
     <ProjectReference Include="../../../src/__Libraries/StellaOps.Canonical.Json/StellaOps.Canonical.Json.csproj" />
-  </ItemGroup>
 
+    <!-- Determinism manifest writer/reader (NEW for SPRINT_5100_0007_0003) -->
+    <ProjectReference Include="../../../src/__Libraries/StellaOps.Testing.Determinism/StellaOps.Testing.Determinism.csproj" />
+  </ItemGroup>
   <ItemGroup>
     <!-- Determinism corpus -->
     <Content Include="../../../bench/determinism/**/*">