feat: Add RustFS artifact object store and migration tool

- Implemented RustFsArtifactObjectStore for managing artifacts in RustFS.
- Added unit tests for RustFsArtifactObjectStore functionality.
- Created a RustFS migrator tool to transfer objects from S3 to RustFS.
- Introduced policy preview and report models for API integration.
- Added fixtures and tests for policy preview and report functionality.
- Included necessary metadata and scripts for cache_pkg package.

bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers.Tests/BenchmarkJsonWriterTests.cs

@@ -0,0 +1,41 @@
+using System.Text.Json;
+using StellaOps.Bench.ScannerAnalyzers;
+using StellaOps.Bench.ScannerAnalyzers.Baseline;
+using StellaOps.Bench.ScannerAnalyzers.Reporting;
+using Xunit;
+
+namespace StellaOps.Bench.ScannerAnalyzers.Tests;
+
+public sealed class BenchmarkJsonWriterTests
+{
+    [Fact]
+    public async Task WriteAsync_EmitsMetadataAndScenarioDetails()
+    {
+        var metadata = new BenchmarkJsonMetadata("1.0", DateTimeOffset.Parse("2025-10-23T12:00:00Z"), "abc123", "ci");
+        var result = new ScenarioResult(
+            "scenario",
+            "Scenario",
+            SampleCount: 5,
+            MeanMs: 10,
+            P95Ms: 12,
+            MaxMs: 20,
+            Iterations: 5,
+            ThresholdMs: 5000);
+        var baseline = new BaselineEntry("scenario", 5, 5, 9, 11, 10);
+        var report = new BenchmarkScenarioReport(result, baseline, 1.2);
+
+        var path = Path.Combine(Path.GetTempPath(), $"bench-{Guid.NewGuid():N}.json");
+        await BenchmarkJsonWriter.WriteAsync(path, metadata, new[] { report }, CancellationToken.None);
+
+        using var document = JsonDocument.Parse(await File.ReadAllTextAsync(path));
+        var root = document.RootElement;
+
+        Assert.Equal("1.0", root.GetProperty("schemaVersion").GetString());
+        Assert.Equal("abc123", root.GetProperty("commit").GetString());
+        var scenario = root.GetProperty("scenarios")[0];
+        Assert.Equal("scenario", scenario.GetProperty("id").GetString());
+        Assert.Equal(20, scenario.GetProperty("maxMs").GetDouble());
+        Assert.Equal(10, scenario.GetProperty("baseline").GetProperty("maxMs").GetDouble());
+        Assert.True(scenario.GetProperty("regression").GetProperty("breached").GetBoolean());
+    }
+}