⚡ Bolt: index_middle 문자열 연결 성능 최적화 (O(N^2) -> O(N))

[seonghobae]

💡 What: index_middle 함수 내부 반복문의 HTML 문자열 병합 방식을 += 연산자에서 StringBuilder로 변경했습니다.
🎯 Why: 기존 += 연산자는 반복문 내에서 사용할 경우 매번 새로운 String 객체를 생성하여 O(N^2)의 복사 오버헤드와 메모리 할당 문제를 일으켰습니다. 디렉토리 내 파일 개수가 많아질수록 성능 저하 폭이 커집니다.
📊 Impact: 문자열 연산 복잡도를 O(N^2)에서 O(N)으로 개선하여 대규모 디렉토리 렌더링 시 응답 시간을 현저히 줄이고 메모리 사용량을 감소시켰습니다.
🔬 Measurement: Jacoco 테스트 커버리지 100%를 유지하도록 수정 및 테스트(읽기 권한 없는 디렉토리에 대한 null 분기 처리 테스트 등)를 완료했습니다.

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PR created automatically by Jules for task 531450353862914154 started by @seonghobae

[google-labs-jules]

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[seonghobae]

Closing as superseded by already-merged StringBuilder optimization (#21). Current master already avoids O(N^2) listing-string concatenation while keeping newer security/accessibility/CSP changes.

[google-labs-jules]

Closing as superseded by already-merged StringBuilder optimization (#21). Current master already avoids O(N^2) listing-string concatenation while keeping newer security/accessibility/CSP changes.

Understood. Acknowledging that this work is now superseded by already-merged StringBuilder optimization and stopping work on this task.