feat: implement XML extraction utilities and enhance feature handling

- Introduced a new xml-extractor module with functions for XML parsing, including escaping/unescaping XML characters, extracting sections and elements, and managing implemented features.
- Added functionality to add, remove, update, and check for implemented features in the app_spec.txt file.
- Enhanced the create and update feature handlers to check for duplicate titles and trigger synchronization with app_spec.txt on status changes.
- Updated tests to cover new XML extraction utilities and feature handling logic, ensuring robust functionality and reliability.

apps/server/src/services/auto-mode-service.ts

@@ -2101,6 +2101,16 @@ Format your response as a structured markdown document.`;
         feature.justFinishedAt = undefined;
       }
       await secureFs.writeFile(featurePath, JSON.stringify(feature, null, 2));
+
+      // Sync completed/verified features to app_spec.txt
+      if (status === 'verified' || status === 'completed') {
+        try {
+          await this.featureLoader.syncFeatureToAppSpec(projectPath, feature);
+        } catch (syncError) {
+          // Log but don't fail the status update if sync fails
+          logger.warn(`Failed to sync feature ${featureId} to app_spec.txt:`, syncError);
+        }
+      }
     } catch {
       // Feature file may not exist
     }