Feature Request: Add GUI Kanban Board Workflow for Planning Reviews

It would be highly valuable to add a graphical Kanban board interface to gstack for managing the planning and review workflow. The board should have the following columns:

- **Backlog:** Where new ideas/tasks are loaded
- **CEO Review:** Tasks are dragged here to trigger `/plan-ceo-review`
- **Engineer Review:** Tasks are dragged here to trigger `/plan-eng-review`
- (Other columns as appropriate for your workflow)

**Desired Features:**

- **Drag-and-drop:** Users can move tasks/ideas between columns using drag-and-drop.
- **Command Integration:** Moving a card to a designated column (e.g., "CEO Review" or "Engineer Review") should automatically kick off the corresponding command (`/plan-ceo-review`, `/plan-eng-review`, etc.).
- **Live Status:** Users can see the status/progress as each command runs, with tasks visually updating in their respective columns.
- **Manual Control:** After each step/review is completed, the human user can decide which column to move the task to next — preserving full human-in-the-loop control of the process.

**Why:**
This improvement would enable a much more intuitive, visual, and interactive planning process, integrating seamlessly with the command triggers already present in gstack. It provides a clear overview of workflow state, empowers users to direct the process, and brings the power of Kanban methodology to gstack's planning review pipeline.