refactor(tasks): Align add-task with unified AI service and add research flag

scripts/modules/task-manager/add-subtask.js

@@ -1,6 +1,8 @@
 import path from 'path';
 
 import { log, readJSON, writeJSON } from '../utils.js';
+import { isTaskDependentOn } from '../task-manager.js';
+import generateTaskFiles from './generate-task-files.js';
 
 /**
  * Add a subtask to a parent task