Problem

When a child Kanban task's status is set to "ready" via the dashboard API (drag-drop or PATCH), the _set_status_direct function accepts it unconditionally — even when the task's parent(s) are still todo, running, or blocked. The dispatcher then spawns the child, which discovers no upstream output and either blocks itself (wasting a spawn cycle) or works with incomplete/stale data.

The dependency guard already exists in recompute_ready (which auto-promotes todo → ready only when all parents are done), but direct status writes via the dashboard bypass this check entirely.

Proposed Fix

Add the same parent-dependency check to _set_status_direct() in plugins/kanban/dashboard/plugin_api.py:

• When new_status == "ready", query all parents and reject (return False → 409) if any parent is not done.
• No change to recompute_ready — it already handles this correctly.
• Update affected tests accordingly.

Impact

• Prevents mis-dispatched tasks from being spawned with unfinished upstream dependencies.
• No breaking change to the dashboard UX — tasks with incomplete parents were never supposed to be draggable to the ready column.