feat: task center - human task interaction, artifact view, restart capability
- Add human task dspy: human_complete, human_list, approval_approve, approval_reject
- Add task_restart.dspy for restarting completed/failed tasks
- Enhance task_detail.ui: inline human task forms, approval buttons, restart
- New step_panel.ui: view/modify step artifacts with cascade rerun
- Update task_list.ui: Tabular with search_form filter by pipeline/state
- Update index.ui: embed task list Tabular inline
- Update load_path.py: register new dspy/ui paths
yumoqing
b556ab0cdc