DSH Task Board: Session Task Board and Parent-Child Task Tree Plugin

The `dsh-task-board` plugin adds visual task management capabilities to DeepSeek Harness (DSH). It provides a canvas-based Kanban board, a parent-child task tree model, and Agent tools, supporting local JSON storage, automatic backups, and version control. Users can install it via the command line, manage tasks in session views, and interact with them through Agent tools, making it well suited for developers who need granular breakdowns of Agent behavior paths.