feat(04-01): scaffold Winter-shaped plugins with generated registry

Render plugin.go, routes.go, leaf packages and go.mod from embedded
templates, emit empty registry accessors, and define job, admin, lang
and mail capability contracts so a new plugin compiles before artifacts.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/build/build_test.go

@@ -337,17 +337,83 @@ func TestParseManifestRejectsUppercaseID(t *testing.T) {
 	}
 }
 
+func TestScaffoldPluginSmoke(t *testing.T) {
+	dir := copyHelloApp(t)
+	ctx := t.Context()
+
+	pluginDir, err := MakePlugin(ctx, dir, "golem15.demo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	assertScaffoldFiles(t, pluginDir)
+
+	pluginSrc, err := os.ReadFile(filepath.Join(pluginDir, "plugin.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	regSrc, err := os.ReadFile(filepath.Join(pluginDir, "registry.gen.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{
+		"generatedModels()",
+		"generatedMigrations()",
+		"generatedCommands()",
+		"generatedJobs()",
+		"generatedAdminControllers()",
+		"//go:embed config",
+		"//go:embed lang",
+		"//go:embed views/mail",
+	} {
+		if !bytes.Contains(pluginSrc, []byte(want)) {
+			t.Fatalf("plugin.go missing %s:\n%s", want, pluginSrc)
+		}
+	}
+	for _, want := range []string{
+		"func generatedModels()",
+		"func generatedMigrations()",
+		"func generatedCommands()",
+		"func generatedJobs()",
+		"func generatedAdminControllers()",
+	} {
+		if !bytes.Contains(regSrc, []byte(want)) {
+			t.Fatalf("registry.gen.go missing %s:\n%s", want, regSrc)
+		}
+	}
+
+	if err := AddPlugin(ctx, dir, filepath.Join("plugins", "demo")); err != nil {
+		t.Fatal(err)
+	}
+	var buf bytes.Buffer
+	if err := App(ctx, dir, &buf); err != nil {
+		t.Fatalf("app build: %v\n%s", err, buf.String())
+	}
+
+	vet := execGo(t, pluginDir, "vet", "./...")
+	if out, err := vet.CombinedOutput(); err != nil {
+		t.Fatalf("plugin go vet: %v\n%s", err, out)
+	}
+
+	pluginAfter, err := os.ReadFile(filepath.Join(pluginDir, "plugin.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(pluginSrc, pluginAfter) {
+		t.Fatal("hand-written plugin.go was rewritten")
+	}
+	regAfter, err := os.ReadFile(filepath.Join(pluginDir, "registry.gen.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(regSrc, regAfter) {
+		t.Fatal("registry.gen.go is not byte-stable after add/build")
+	}
+}
+
 func assertScaffoldFiles(t *testing.T, pluginDir string) {
 	t.Helper()
-	if _, err := os.Stat(filepath.Join(pluginDir, "go.mod")); err != nil {
-		t.Fatal(err)
-	}
-	if _, err := os.Stat(filepath.Join(pluginDir, "plugin.go")); err != nil {
-		t.Fatal(err)
-	}
-	if _, err := os.Stat(filepath.Join(pluginDir, "config")); err != nil {
-		t.Fatal(err)
-	}
+	assertWinterPluginShape(t, pluginDir)
+
 	body, err := os.ReadFile(filepath.Join(pluginDir, "plugin.go"))
 	if err != nil {
 		t.Fatal(err)
@@ -375,6 +441,36 @@ func assertScaffoldFiles(t *testing.T, pluginDir string) {
 		t.Fatalf("plugin go.mod missing module path:\n%s", mod)
 	}
 
+	cmd := execGo(t, pluginDir, "build", "./...")
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("plugin does not compile: %v\n%s", err, out)
+	}
+}
+
+func assertWinterPluginShape(t *testing.T, pluginDir string) {
+	t.Helper()
+	required := []string{
+		"go.mod",
+		"plugin.go",
+		"routes.go",
+		"registry.gen.go",
+		filepath.Join("config", "config.yaml"),
+		filepath.Join("lang", "en", "lang.yaml"),
+		filepath.Join("views", "mail", "welcome.htm"),
+	}
+	for _, leaf := range pluginLeaves {
+		required = append(required, filepath.Join(leaf, "doc.go"))
+	}
+	allowed := map[string]struct{}{
+		"go.sum": {},
+	}
+	for _, rel := range required {
+		allowed[rel] = struct{}{}
+		if _, err := os.Stat(filepath.Join(pluginDir, rel)); err != nil {
+			t.Fatalf("missing %s: %v", rel, err)
+		}
+	}
+
 	var extra []string
 	if err := filepath.WalkDir(pluginDir, func(path string, d os.DirEntry, err error) error {
 		if err != nil {
@@ -387,13 +483,15 @@ func assertScaffoldFiles(t *testing.T, pluginDir string) {
 		if err != nil {
 			return err
 		}
-		switch rel {
-		case "go.mod", "go.sum", "plugin.go", filepath.Join("config", ".gitkeep"):
+		if _, ok := allowed[rel]; ok {
 			return nil
-		default:
+		}
+		if strings.HasPrefix(filepath.Base(rel), "registry.gen.go.") {
 			extra = append(extra, rel)
 			return nil
 		}
+		extra = append(extra, rel)
+		return nil
 	}); err != nil {
 		t.Fatal(err)
 	}
@@ -401,9 +499,14 @@ func assertScaffoldFiles(t *testing.T, pluginDir string) {
 		t.Fatalf("unexpected scaffold files: %v", extra)
 	}
 
-	cmd := execGo(t, pluginDir, "build", "-o", filepath.Join(pluginDir, "demo.bin"), ".")
-	if out, err := cmd.CombinedOutput(); err != nil {
-		t.Fatalf("plugin does not compile: %v\n%s", err, out)
+	for _, asset := range []string{
+		filepath.Join("config", "config.yaml"),
+		filepath.Join("lang", "en", "lang.yaml"),
+		filepath.Join("views", "mail", "welcome.htm"),
+	} {
+		if strings.HasPrefix(filepath.Base(asset), ".") || strings.HasPrefix(filepath.Base(asset), "_") {
+			t.Fatalf("embed-incompatible hidden asset %s", asset)
+		}
 	}
 }