- Add parentTaskId, childTaskIds, and taskStatus fields to HistoryItem schema
- Remove in-memory task stack (clineStack) from ClineProvider
- Replace polling mechanism with direct task resumption
- Update task persistence to include new relationship fields
- Implement persistent task management using task status field
This refactor eliminates CPU waste from polling, simplifies code by removing
unnecessary complexity, enables task resumption after system restarts, and
provides a foundation for task tree visualization.
Fixes#6672