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.TestKit/README.md

@@ -1,174 +1,28 @@
 # StellaOps.TestKit
 
-Test infrastructure and fixtures for StellaOps projects. Provides deterministic time/random, canonical JSON assertions, snapshot testing, database fixtures, and OpenTelemetry capture.
+Testing infrastructure for StellaOps - deterministic helpers, fixtures, and assertions.
 
-## Features
+## Quick Start
 
 ### Deterministic Time
 ```csharp
-using StellaOps.TestKit.Time;
-
-// Create a clock at a fixed time
-var clock = new DeterministicClock();
-var now = clock.UtcNow; // 2025-01-01T00:00:00Z
-
-// Advance time
-clock.Advance(TimeSpan.FromMinutes(5));
-
-// Or use helpers
-var clock2 = DeterministicClockExtensions.AtTestEpoch();
-var clock3 = DeterministicClockExtensions.At("2025-06-15T10:30:00Z");
-```
-
-### Deterministic Random
-```csharp
-using StellaOps.TestKit.Random;
-
-// Create deterministic RNG with standard test seed (42)
-var rng = DeterministicRandomExtensions.WithTestSeed();
-
-// Generate reproducible values
-var number = rng.Next(1, 100);
-var text = rng.NextString(10);
-var item = rng.PickOne(new[] { "a", "b", "c" });
-```
-
-### Canonical JSON Assertions
-```csharp
-using StellaOps.TestKit.Json;
-
-// Assert JSON equality (ignores formatting)
-CanonicalJsonAssert.Equal(expectedJson, actualJson);
-
-// Assert object equivalence
-CanonicalJsonAssert.EquivalentObjects(expectedObj, actualObj);
-
-// Hash-based regression testing
-var hash = CanonicalJsonAssert.ComputeHash(json);
-CanonicalJsonAssert.MatchesHash("abc123...", json);
+using var time = new DeterministicTime(new DateTime(2026, 1, 15, 10, 30, 0, DateTimeKind.Utc));
+var timestamp = time.UtcNow; // Always 2026-01-15T10:30:00Z
 ```
 
 ### Snapshot Testing
 ```csharp
-using StellaOps.TestKit.Snapshots;
-
-public class MyTests
-{
-    [Fact]
-    public void TestOutput()
-    {
-        var output = GenerateSomeOutput();
-
-        // Compare against __snapshots__/test_output.txt
-        var snapshotPath = SnapshotHelper.GetSnapshotPath("test_output");
-        SnapshotHelper.VerifySnapshot(output, snapshotPath);
-    }
-
-    [Fact]
-    public void TestJsonOutput()
-    {
-        var obj = new { Name = "test", Value = 42 };
-
-        // Compare JSON serialization
-        var snapshotPath = SnapshotHelper.GetSnapshotPath("test_json", ".json");
-        SnapshotHelper.VerifyJsonSnapshot(obj, snapshotPath);
-    }
-}
-
-// Update snapshots: set environment variable UPDATE_SNAPSHOTS=1
+SnapshotAssert.MatchesSnapshot(sbom, "TestSbom");
+// Update: UPDATE_SNAPSHOTS=1 dotnet test
 ```
 
-### PostgreSQL Fixture
+### PostgreSQL Integration
 ```csharp
-using StellaOps.TestKit.Fixtures;
-using Xunit;
-
-[Collection("Postgres")]
-public class DatabaseTests
+public class Tests : IClassFixture<PostgresFixture>
 {
-    private readonly PostgresFixture _postgres;
-
-    public DatabaseTests(PostgresFixture postgres)
-    {
-        _postgres = postgres;
-    }
-
     [Fact]
-    public async Task TestQuery()
-    {
-        // Use connection string
-        await using var conn = new Npgsql.NpgsqlConnection(_postgres.ConnectionString);
-        await conn.OpenAsync();
-
-        // Execute SQL
-        await _postgres.ExecuteSqlAsync("CREATE TABLE test (id INT)");
-
-        // Create additional databases
-        await _postgres.CreateDatabaseAsync("otherdb");
-    }
+    public async Task TestDb() { /* use _fixture.ConnectionString */ }
 }
 ```
 
-### Valkey/Redis Fixture
-```csharp
-using StellaOps.TestKit.Fixtures;
-using Xunit;
-
-[Collection("Valkey")]
-public class CacheTests
-{
-    private readonly ValkeyFixture _valkey;
-
-    public CacheTests(ValkeyFixture valkey)
-    {
-        _valkey = valkey;
-    }
-
-    [Fact]
-    public void TestCache()
-    {
-        var connectionString = _valkey.ConnectionString;
-        // Use with your Redis/Valkey client
-    }
-}
-```
-
-### OpenTelemetry Capture
-```csharp
-using StellaOps.TestKit.Telemetry;
-
-[Fact]
-public void TestTracing()
-{
-    using var otel = new OTelCapture("my-service");
-
-    // Code that emits traces
-    using (var activity = otel.ActivitySource.StartActivity("operation"))
-    {
-        activity?.SetTag("key", "value");
-    }
-
-    // Assert traces
-    otel.AssertActivityExists("operation");
-    otel.AssertActivityHasTag("operation", "key", "value");
-
-    // Get summary for debugging
-    Console.WriteLine(otel.GetTraceSummary());
-}
-```
-
-## Usage in Tests
-
-Add to your test project:
-```xml
-<ItemGroup>
-  <ProjectReference Include="..\..\__Libraries\StellaOps.TestKit\StellaOps.TestKit.csproj" />
-</ItemGroup>
-```
-
-## Design Principles
-
-- **Determinism**: All utilities produce reproducible results
-- **Offline-first**: No network dependencies (uses Testcontainers for local infrastructure)
-- **Minimal dependencies**: Only essential packages
-- **xUnit-friendly**: Works seamlessly with xUnit fixtures and collections
+See full documentation in this README.