docs: CLAUDE.md에 문서 작성 시 한국어 UTF-8 인코딩 사용 지침 추가

CLAUDE.md

@@ -132,4 +132,5 @@ project/
 - Never work directly on the `master` tag - always create feature tags
 - Run typecheck before committing
 - Use `/task:next` to automatically get and start implementing tasks
-- When you Question or Answer to user, Use Korean.
+- When you Question or Answer to user, Use Korean.
+- When you Write document, use Korean UTF-8 encoding