refactor(tasks): Align update-tasks with unified AI service and remove obsolete helpers

Completes the refactoring of the AI-interacting task management functions by aligning `update-tasks.js` with the unified service architecture and removing now-unused helper files.

Key Changes:

- **`update-tasks.js` Refactoring:**

    - Replaced direct AI client calls and AI-specific config fetching with a call to `generateTextService` from `ai-services-unified.js`.

    - Preserved the original system and user prompts requesting a JSON array output.

    - Implemented manual JSON parsing (`parseUpdatedTasksFromText`) with Zod validation to handle the text response reliably.

    - Updated the core function signature to accept the standard `context` object (`{ session, mcpLog }`).

    - Corrected logger implementation to handle both MCP (`mcpLog`) and CLI (`consoleLog`) contexts appropriately.

- **Related Component Updates:**

    - Refactored `mcp-server/src/core/direct-functions/update-tasks.js` to use the standard direct function pattern (logger wrapper, silent mode, call core function with context).

    - Verified `mcp-server/src/tools/update.js` correctly passes arguments and context.

    - Verified `scripts/modules/commands.js` (update command) correctly calls the refactored core function.

- **Obsolete File Cleanup:**

    - Removed the now-unused `scripts/modules/task-manager/get-subtasks-from-ai.js` file and its export, as its functionality was integrated into `expand-task.js`.

    - Removed the now-unused `scripts/modules/task-manager/generate-subtask-prompt.js` file and its export for the same reason.

- **Task Management:**

    - Marked subtasks 61.38, 61.39, and 61.41 as complete.

This commit finalizes the alignment of `updateTasks`, `updateTaskById`, `expandTask`, `expandAllTasks`, `analyzeTaskComplexity`, `addTask`, and `parsePRD` with the unified AI service and configuration management patterns.

scripts/modules/task-manager.js

@@ -22,8 +22,6 @@ import removeSubtask from './task-manager/remove-subtask.js';
 import updateSubtaskById from './task-manager/update-subtask-by-id.js';
 import removeTask from './task-manager/remove-task.js';
 import taskExists from './task-manager/task-exists.js';
-import generateSubtaskPrompt from './task-manager/generate-subtask-prompt.js';
-import getSubtasksFromAI from './task-manager/get-subtasks-from-ai.js';
 import isTaskDependentOn from './task-manager/is-task-dependent.js';
 
 // Export task manager functions
@@ -47,7 +45,5 @@ export {
 	removeTask,
 	findTaskById,
 	taskExists,
-	generateSubtaskPrompt,
-	getSubtasksFromAI,
 	isTaskDependentOn
 };