Add public local bundle writer

pkg/bundle/example_test.go

@@ -38,3 +38,36 @@ func ExampleBuildManifest() {
 	// report.txt
 	// 7
 }
+
+func ExampleWriteBundle() {
+	sourceRoot, err := os.MkdirTemp("", "distributor-source-*")
+	if err != nil {
+		panic(err)
+	}
+	defer os.RemoveAll(sourceRoot)
+	outputRoot := filepath.Join(os.TempDir(), "distributor-bundle-example")
+	defer os.RemoveAll(outputRoot)
+
+	if err := os.WriteFile(filepath.Join(sourceRoot, "report.txt"), []byte("report\n"), 0o600); err != nil {
+		panic(err)
+	}
+
+	manifest, err := bundle.WriteBundle(bundle.WriteBundleOptions{
+		Root:    outputRoot,
+		ID:      "reports.example",
+		Created: time.Date(2026, 5, 30, 11, 10, 0, 0, time.UTC),
+		Files: []bundle.BundleFile{
+			{SourcePath: filepath.Join(sourceRoot, "report.txt"), Path: "report.txt"},
+		},
+		Overwrite: true,
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(manifest.ID)
+	fmt.Println(manifest.Files[0].Path)
+	// Output:
+	// reports.example
+	// report.txt
+}