Update existing pull request title and description based on latest changes.
Use when user wants to refresh PR with latest commits. Triggers include:
- Korean: "PR 업데이트해줘", "PR 수정해줘", "PR 다시 만들어줘"
- English: "update PR", "refresh PR", "regenerate PR description"
- Context: User has existing PR and wants to update title/description after adding more commits