### Type of change - [x] Refactoring
### What problem does this PR solve? Removed set_entity and set_relation to avoid accessing doc engine during graph computation. Introduced GraphChange to avoid writing unchanged chunks. ### Type of change - [x] Performance Improvement
fix: issue https://github.com/infiniflow/ragflow/issues/5600 ### What problem does this PR solve? close issue https://github.com/infiniflow/ragflow/issues/5600 ### Type of change - [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve? #4543 ### Type of change - [x] New Feature (non-breaking change which adds functionality)