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.

src/__Libraries/StellaOps.Cryptography/CryptoProvider.cs

@@ -53,7 +53,8 @@ public interface ICryptoProvider
     /// <param name="algorithmId">Signing algorithm identifier (e.g., RS256, ES256).</param>
     /// <param name="publicKeyBytes">Public key in SubjectPublicKeyInfo format (DER-encoded).</param>
     /// <returns>Ephemeral signer instance (supports VerifyAsync only).</returns>
-    ICryptoSigner CreateEphemeralVerifier(string algorithmId, ReadOnlySpan<byte> publicKeyBytes);
+    ICryptoSigner CreateEphemeralVerifier(string algorithmId, ReadOnlySpan<byte> publicKeyBytes)
+        => throw new NotSupportedException($"Provider '{Name}' does not support ephemeral verification.");
 
     /// <summary>
     /// Adds or replaces signing key material managed by this provider.