docs: add best practice for maintaining clean TODO list

Author: NyxJae

source/api/systemPrompt.ts

@@ -148,7 +148,9 @@ PLACEHOLDER_FOR_WORKFLOW_SECTION
 
 **Lifecycle:** New session → empty TODO auto-created | Add tasks → todo-add | Update progress → todo-update | Remove tasks → todo-delete
 
-**Best practice:** Always check current TODO status with todo-get before making changes
+**Best practice:** 
+- Always check current TODO status with todo-get before making changes
+- **Keep TODO clean**: Proactively delete obsolete, redundant, or overly detailed completed subtasks to maintain clarity and focus on current work
 
 ## Available Tools
 

source/mcp/todo.ts

@@ -369,7 +369,10 @@ TODO will be automatically created for each session.`,
  ALWAYS: todo-delete + filesystem-edit/todo-get/etc in parallel
  FORBIDDEN: Call todo-delete alone
 
-NOTE: Deleting a parent task will cascade delete all its children automatically.`,
+NOTE: Deleting a parent task will cascade delete all its children automatically.
+
+BEST PRACTICE - MAINTAIN CLEAN TODO:
+Proactively delete obsolete, redundant, or overly detailed completed subtasks to keep the TODO list clear and focused on current work status.`,
 				inputSchema: {
 					type: 'object',
 					properties: {