feat(sdk): add Kind and Categories to ModPlugin; writeMod emits them

cmd/ninja/cmd/plugin.go

@@ -503,6 +503,16 @@ func writeMod(path string, m *core.ModFile) error {
 	b.WriteString(fmt.Sprintf("name = %q\n", m.Plugin.Name))
 	b.WriteString(fmt.Sprintf("scope = %q\n", m.Plugin.Scope))
 	b.WriteString(fmt.Sprintf("version = %q\n", m.Plugin.Version))
+	if m.Plugin.Kind != "" {
+		b.WriteString(fmt.Sprintf("kind = %q\n", m.Plugin.Kind))
+	}
+	if len(m.Plugin.Categories) > 0 {
+		quoted := make([]string, len(m.Plugin.Categories))
+		for i, c := range m.Plugin.Categories {
+			quoted[i] = fmt.Sprintf("%q", c)
+		}
+		b.WriteString(fmt.Sprintf("categories = [%s]\n", strings.Join(quoted, ", ")))
+	}
 	if m.Compatibility != nil {
 		b.WriteString("\n[compatibility]\n")
 		b.WriteString(fmt.Sprintf("block_core = %q\n", m.Compatibility.BlockCore))

plugin/mod.go

@@ -14,6 +14,8 @@ type ModPlugin struct {
 	Name       string   `toml:"name"`
 	Scope      string   `toml:"scope"`
 	Version    string   `toml:"version"`
+	Kind       string   `toml:"kind,omitempty"`
+	Categories []string `toml:"categories,omitempty"`
 }
 
 type ModCompat struct {

plugin/mod_test.go

@@ -64,6 +64,42 @@ func TestParseModFull_EmptyInput(t *testing.T) {
 	}
 }
 
+func TestParseModFull_KindAndCategories(t *testing.T) {
+	src := []byte(`
+[plugin]
+name = "analyser"
+scope = "blockninja"
+version = "0.1.0"
+kind = "plugin"
+categories = ["analytics", "seo"]
+`)
+	m, err := ParseModFull(src)
+	if err != nil {
+		t.Fatalf("ParseModFull err: %v", err)
+	}
+	if m.Plugin.Kind != "plugin" {
+		t.Errorf("Kind = %q, want plugin", m.Plugin.Kind)
+	}
+	if got := m.Plugin.Categories; len(got) != 2 || got[0] != "analytics" || got[1] != "seo" {
+		t.Errorf("Categories = %v", got)
+	}
+}
+
+func TestParseModFull_KindDefaultsEmpty(t *testing.T) {
+	src := []byte(`
+[plugin]
+name = "legacy"
+version = "0.1.0"
+`)
+	m, err := ParseModFull(src)
+	if err != nil {
+		t.Fatalf("ParseModFull err: %v", err)
+	}
+	if m.Plugin.Kind != "" {
+		t.Errorf("Kind should be empty for legacy mod, got %q", m.Plugin.Kind)
+	}
+}
+
 func TestParseModFull_RequiresAndCompat(t *testing.T) {
 	src := []byte(`
 [plugin]