⚡ Bolt: [성능 개선] content-visibility 적용을 통한 렌더링 지연 및 초기 로딩 속도 개선

[seonghobae]

• 💡 What: styles.css의 .section 클래스에 content-visibility: auto와 contain-intrinsic-size: auto 600px 속성 추가.
• 🎯 Why: 긴 단일 페이지에서 뷰포트 바깥의 DOM 요소들까지 초기 로딩 시 한 번에 렌더링되어 초기 렌더링 지연이 발생하는 문제를 해결하기 위함.
• 📊 Impact: 브라우저가 화면 밖 섹션의 Layout/Paint 연산을 생략하므로 초기 렌더링 시간 단축 (DOM 노드가 많은 경우 렌더링 부하 최대 ~30-50% 감소 예상).
• 🔬 Measurement: Chrome DevTools의 Performance 탭에서 Layout/Paint 시간 단축 측정, 또는 Rendering 탭에서 "Paint flashing"을 켜고 스크롤 시 화면 밖 요소들의 페인트 발생 확인.

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PR created automatically by Jules for task 10651559521516177657 started by @seonghobae

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[Copilot]

Pull request overview

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긴 단일 페이지에서 뷰포트 밖 섹션의 초기 렌더링 비용을 줄이기 위해, .section에 content-visibility 기반의 지연 렌더링을 적용한 PR입니다.

Changes:

• .section에 content-visibility: auto 및 contain-intrinsic-size 추가로 오프스크린 렌더링 비용 절감
• 변경 사항을 CHANGELOG.md 및 .jules/bolt.md에 문서화

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
styles.css	.section에 content-visibility/contain-intrinsic-size를 추가해 초기 Layout/Paint 부담을 줄임
CHANGELOG.md	성능 개선 사항(오프스크린 렌더링 최적화)을 Unreleased 항목에 기록
.jules/bolt.md	성능 최적화 학습/액션 로그에 content-visibility 적용 경험을 추가

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