- Add reasoning delta processing to vLLM adapter Execute function
- Use choice.Delta.ReasoningText() to handle both reasoning_content and reasoning fields
- Align vLLM behavior with openai_compat adapter
- Update CODE_REVIEW verification output with new test results
- Document plan deviation in 计划 대비 변경 사항 section
Closes inconsistency with PLAN requirement: 'reasoning/tool delta와 cancel을 보존한다'
