feat(core): DartExtractor — enum declarations

Adds enum_declaration handling to DartExtractor: enum constants are surfaced
as properties[] so the structural graph captures Color.red / Color.green etc.
Implements Task 9 of the Dart language support plan (TDD, 16/16 dart tests
pass, full suite 708/708).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

understand-anything-plugin/packages/core/src/plugins/extractors/__tests__/dart-extractor.test.ts

@@ -220,6 +220,19 @@ describe("DartExtractor", () => {
     });
   });
 
+  describe("extractStructure - enums", () => {
+    it("extracts a simple enum and surfaces its constants as properties", () => {
+      const { tree, parser, root } = parse(`enum Color { red, green, blue }\n`);
+      const result = extractor.extractStructure(root);
+
+      expect(result.classes).toHaveLength(1);
+      expect(result.classes[0].name).toBe("Color");
+      expect(result.classes[0].properties).toEqual(["red", "green", "blue"]);
+      tree.delete();
+      parser.delete();
+    });
+  });
+
   describe("extractStructure - extensions", () => {
     it("extracts a named extension on String", () => {
       const { tree, parser, root } = parse(`extension StringX on String {

understand-anything-plugin/packages/core/src/plugins/extractors/dart-extractor.ts

@@ -241,6 +241,9 @@ export class DartExtractor implements LanguageExtractor {
         case "extension_declaration":
           this.extractExtensionDeclaration(node, classes, functions, exports);
           break;
+        case "enum_declaration":
+          this.extractEnumDeclaration(node, classes, exports);
+          break;
       }
     }
 
@@ -348,6 +351,36 @@ export class DartExtractor implements LanguageExtractor {
     );
   }
 
+  private extractEnumDeclaration(
+    declNode: TreeSitterNode,
+    classes: StructuralAnalysis["classes"],
+    exports: StructuralAnalysis["exports"],
+  ): void {
+    const nameNode = findChild(declNode, "identifier");
+    if (!nameNode) return;
+    const name = nameNode.text;
+
+    const properties: string[] = [];
+    const body = findChild(declNode, "enum_body");
+    if (body) {
+      for (const k of findChildren(body, "enum_constant")) {
+        const id = findChild(k, "identifier");
+        if (id) properties.push(id.text);
+      }
+    }
+
+    classes.push({
+      name,
+      lineRange: [declNode.startPosition.row + 1, declNode.endPosition.row + 1],
+      methods: [],
+      properties,
+    });
+
+    if (isExported(name)) {
+      exports.push({ name, lineNumber: declNode.startPosition.row + 1 });
+    }
+  }
+
   extractCallGraph(rootNode: TreeSitterNode): CallGraphEntry[] {
     // Implementation lands in a later task.
     void rootNode;