fix: correct command references in implement.md

Update speckit.implement.md to correct the command for regenerating the task list from '/tasks' to '/speckit.tasks', ensuring accurate documentation for task breakdown requirements.

Author: JianfuLi

templates/commands/implement.md

@@ -128,5 +128,5 @@ You **MUST** consider the user input before proceeding (if not empty).
    - Confirm the implementation follows the technical plan
    - Report final status with summary of completed work
 
-Note: This command assumes a complete task breakdown exists in tasks.md. If tasks are incomplete or missing, suggest running `/tasks` first to regenerate the task list.
+Note: This command assumes a complete task breakdown exists in tasks.md. If tasks are incomplete or missing, suggest running `/speckit.tasks` first to regenerate the task list.