Add impact index fixture and filesystem artifact uploader

- Introduced a sample BOM index JSON file for impact index testing.
- Created unit tests for the impact index fixture to ensure proper loading of sample images.
- Implemented the FilesystemPackRunArtifactUploader class to handle artifact uploads to the local filesystem.
- Added comprehensive tests for the FilesystemPackRunArtifactUploader, covering file copying, missing files, and expression outputs.

src/Scheduler/__Tests/StellaOps.Scheduler.WebService.Tests/ImpactIndexFixtureTests.cs

@@ -0,0 +1,52 @@
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging.Abstractions;
+using StellaOps.Scheduler.ImpactIndex;
+using StellaOps.Scheduler.Models;
+using Xunit;
+
+namespace StellaOps.Scheduler.WebService.Tests;
+
+public sealed class ImpactIndexFixtureTests
+{
+    [Fact]
+    public void FixtureDirectoryExists()
+    {
+        var fixtureDirectory = GetFixtureDirectory();
+        Assert.True(Directory.Exists(fixtureDirectory), $"Fixture directory not found: {fixtureDirectory}");
+
+        var files = Directory.EnumerateFiles(fixtureDirectory, "bom-index.json", SearchOption.AllDirectories).ToArray();
+        Assert.NotEmpty(files);
+
+        var sampleFile = Path.Combine(fixtureDirectory, "sample", "bom-index.json");
+        Assert.Contains(sampleFile, files);
+    }
+
+    [Fact]
+    public async Task FixtureImpactIndexLoadsSampleImage()
+    {
+        var fixtureDirectory = GetFixtureDirectory();
+        var options = new ImpactIndexStubOptions
+        {
+            FixtureDirectory = fixtureDirectory,
+            SnapshotId = "tests/impact-index-stub"
+        };
+
+        var index = new FixtureImpactIndex(options, TimeProvider.System, NullLogger<FixtureImpactIndex>.Instance);
+        var selector = new Selector(SelectorScope.AllImages);
+
+        var impactSet = await index.ResolveAllAsync(selector, usageOnly: false);
+
+        Assert.True(impactSet.Total > 0, "Expected the fixture impact index to load at least one image.");
+    }
+
+    private static string GetFixtureDirectory()
+    {
+        var assemblyLocation = typeof(SchedulerWebApplicationFactory).Assembly.Location;
+        var assemblyDirectory = Path.GetDirectoryName(assemblyLocation)
+            ?? AppContext.BaseDirectory;
+
+        return Path.GetFullPath(Path.Combine(assemblyDirectory, "seed-data", "impact-index"));
+    }
+}