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/PrometheusWriterTests.cs

@@ -0,0 +1,32 @@
+using StellaOps.Bench.ScannerAnalyzers;
+using StellaOps.Bench.ScannerAnalyzers.Baseline;
+using StellaOps.Bench.ScannerAnalyzers.Reporting;
+using Xunit;
+
+namespace StellaOps.Bench.ScannerAnalyzers.Tests;
+
+public sealed class PrometheusWriterTests
+{
+    [Fact]
+    public void Write_EmitsMetricsForScenario()
+    {
+        var result = new ScenarioResult(
+            "scenario_a",
+            "Scenario A",
+            SampleCount: 5,
+            MeanMs: 10,
+            P95Ms: 12,
+            MaxMs: 20,
+            Iterations: 5,
+            ThresholdMs: 5000);
+        var baseline = new BaselineEntry("scenario_a", 5, 5, 9, 11, 18);
+        var report = new BenchmarkScenarioReport(result, baseline, 1.2);
+
+        var path = Path.Combine(Path.GetTempPath(), $"metrics-{Guid.NewGuid():N}.prom");
+        PrometheusWriter.Write(path, new[] { report });
+
+        var contents = File.ReadAllText(path);
+        Assert.Contains("scanner_analyzer_bench_max_ms{scenario=\"scenario_a\"} 20", contents);
+        Assert.Contains("scanner_analyzer_bench_regression_ratio{scenario=\"scenario_a\"}", contents);
+    }
+}