- Add CheckpointService with full CRUD capabilities for task checkpoints
- Support document-level progress tracking and state management
- Implement pause/resume/cancel functionality
- Add retry logic with configurable limits for failed documents
- Track token usage and overall progress
- Include comprehensive unit tests (22 tests)
- Include integration tests with real database (8 tests)
- Add working demo with 4 real-world scenarios
- Add TaskCheckpoint model to database schema
This feature enables RAPTOR and GraphRAG tasks to:
- Recover from crashes without losing progress
- Pause and resume processing
- Automatically retry failed documents
- Track detailed progress and token usage
All tests passing (30/30)
