Add ditto archive helper

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/archive/archive.go

@@ -0,0 +1,22 @@
+package archive
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/leonmika/wails-release/internal/runner"
+)
+
+// ZipApp wraps a .app bundle into a .app.zip via ditto, preserving
+// extended attributes and producing an archive Apple's notary service
+// will accept.
+func ZipApp(ctx context.Context, r runner.Runner, app, zipPath string) error {
+	_, err := r.Run(ctx, runner.Spec{
+		Name: "ditto",
+		Args: []string{"-c", "-k", "--keepParent", app, zipPath},
+	})
+	if err != nil {
+		return fmt.Errorf("ditto archive %s -> %s: %w", app, zipPath, err)
+	}
+	return nil
+}

internal/archive/archive_test.go

@@ -0,0 +1,24 @@
+package archive_test
+
+import (
+	"context"
+	"reflect"
+	"testing"
+
+	"github.com/leonmika/wails-release/internal/archive"
+	"github.com/leonmika/wails-release/internal/runner"
+)
+
+func TestZipApp_BuildsCorrectDittoArgs(t *testing.T) {
+	f := &runner.Fake{}
+	f.On("ditto", nil).Return(nil, nil)
+
+	err := archive.ZipApp(context.Background(), f, "/build/MyApp.app", "/dist/MyApp-1.2.3.app.zip")
+	if err != nil {
+		t.Fatalf("unexpected: %v", err)
+	}
+	want := []string{"-c", "-k", "--keepParent", "/build/MyApp.app", "/dist/MyApp-1.2.3.app.zip"}
+	if !reflect.DeepEqual(f.Calls[0].Args, want) {
+		t.Fatalf("args got %v want %v", f.Calls[0].Args, want)
+	}
+}