Coordinates Waiting -> Queued transitions between sibling subtasks: when a child finishes Done, the next Waiting sibling is promoted to Queued. WorkerHub.QueuePlanningSubtasksAsync exposes this to the UI; TaskRunner advances the chain on completion. Also tightens the planning-session prompt: planner must use MCP tools, not direct edits.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
