dsh-quadrant-todolist: DSH Sidebar Four-Quadrant To-Do Manager

Introducing ziye-jk/dsh-quadrant-todolist: consolidating tasks into the DSH host sidebar, with a shared todos.json for both humans and agents. It covers the Eisenhower Matrix, monthly and weekly views, statistics, system and Feishu notifications, statutory working days, and Ebbinghaus repetition. It explains GitHub source installation commands, configuration options, recurring task behaviors, and personal_todo tool parameters, as well as the self-check sequence and compatibility considerations after upgrading the host.