⚡ Bolt: 세션 타임라인 차트의 날짜 파싱 중복 제거 최적화

[seonghobae]

💡 What: SessionTimelineChart 컴포넌트 렌더링 시 리스트의 크기만큼 반복적으로 실행되던 날짜 문자열 파싱(new Date(u.timestamp).getTime())을 useMemo를 이용해 별도로 분리하고 숫자 배열로 사전 연산하여 캐싱했습니다.

🎯 Why: 리액트 컴포넌트가 다시 렌더링될 때마다 chartData 내부 루프에서 동일한 날짜 문자열을 매번 반복적으로 파싱하고 있었습니다. 이는 배열 크기에 비례하는(O(N)) 불필요한 연산 비용을 발생시켜, 세션 타임라인이 길어질수록 UI 렌더링 병목이 될 수 있습니다.

📊 Impact:

• 차트 렌더링 시 발생하는 문자열 기반의 날짜 생성/파싱 횟수를 렌더링마다 O(2N)에서 의존성 변경 시 O(N)으로 대폭 감소.
• useMemo를 통해 usageTimeline이 변경되지 않는 한 파싱 오버헤드가 완전히 0이 되어, 빠른 컴포넌트 리렌더링 및 부드러운 스크롤 경험을 제공.

🔬 Measurement:

• 차트 렌더링을 포함한 페이지 프로파일링 시 Date 객체 생성 및 문자열 파싱에 소요되는 메인 스레드 실행 시간 측정.
• 데이터가 많은 대규모 세션 페이지(예: 수백 개의 턴)에서 컴포넌트 리렌더링 소요 시간 확인.

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PR created automatically by Jules for task 10493176468770379226 started by @seonghobae

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📒 Files selected for processing (2)

• .jules/bolt.md
• packages/web/src/components/dashboard/session-timeline-chart.tsx

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