- Added `parentToolCallId` and `index` fields to subagent session records and propagated them from task lifecycle and progress events.
- Reworked subagent ordering to sort by parent-group order, spawn index, and stable creation order so out-of-order updates no longer reshuffled active HUD rows.
- Updated task execution to pass spawn indices through sync and async paths, switched the `tool.task` icon to Octicons tasklist, and added a registry test for out-of-order progress ordering.