fix: Copilot AI 2차 코드 리뷰 반영 — 테스트명 수정, 도메인 검증 강화, 코드 품질 개선

Copilot pull-request-reviewer 2차 리뷰 지적 사항을 반영한다.

변경 사항:
- HaversineTest: approxHundredKmBetweenSeoulAndSuwon → approxFortyFiveKmBetweenSeoulAndSuwon
  (메서드명이 실제 검증 거리 ~45km와 불일치하여 수정)
- DateCoursePlace: create() 팩토리 메서드에 sequenceOrder >= 0 검사 추가
  (정렬 키로 사용되는 필드의 도메인 불변식 명시)
- CourseSelector: 선택 루프 후 O(n·m) pool 재조립 → O(n) 직접 구성으로 단순화
  (List.contains/indexOf 대신 선택 시점에 pickedPlaces 직접 누적,
   중복 방지용 picked Set<Long> 별도 유지)
- BusinessHoursAtTimeChecker: java.util.Set FQN → import java.util.Set 추가 후 단순명 사용
  (파일 내 다른 타입과 스타일 통일)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: HHS-kor

src/main/java/com/hufs/capstone/backend/course/application/BusinessHoursAtTimeChecker.java

@@ -5,6 +5,7 @@
 import java.time.Instant;
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
+import java.util.Set;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Component;
 
@@ -14,7 +15,7 @@ public class BusinessHoursAtTimeChecker {
 
 	private static final ZoneId SEOUL_ZONE = ZoneId.of("Asia/Seoul");
 
-	private static final java.util.Set<BusinessStatus> OPEN_STATUSES = java.util.Set.of(
+	private static final Set<BusinessStatus> OPEN_STATUSES = Set.of(
 			BusinessStatus.OPEN,
 			BusinessStatus.OPEN_24_HOURS,
 			BusinessStatus.CLOSING_SOON

src/main/java/com/hufs/capstone/backend/course/application/CourseSelector.java

@@ -35,7 +35,8 @@ CourseSelectionResult select(
 			Instant plannedDateTime
 	) {
 		NormalizationContext ctx = buildNormalizationContext(pool, mode);
-		List<Long> picked = new ArrayList<>();
+		List<RoomPlace> pickedPlaces = new ArrayList<>();
+		Set<Long> pickedIds = new HashSet<>();
 		List<Integer> skipped = new ArrayList<>();
 		AvailableCandidate prev = null;
 
@@ -44,7 +45,7 @@ CourseSelectionResult select(
 			final AvailableCandidate prevForLambda = prev;
 			Optional<AvailableCandidate> best = pool.forSlot(slot).stream()
 					.filter(c -> !globallyUsedIds.contains(c.roomPlace().getId()))
-					.filter(c -> !picked.contains(c.roomPlace().getId()))
+					.filter(c -> !pickedIds.contains(c.roomPlace().getId()))
 					.filter(c -> mode != CourseMode.POPULAR || c.roomPlace().getOriginRoomLink() != null)
 					.max(Comparator.comparingDouble(
 							c -> scorer.score(c, prevForLambda, mode, ctx, plannedDateTime)
@@ -56,17 +57,12 @@ CourseSelectionResult select(
 			}
 
 			AvailableCandidate chosen = best.get();
-			picked.add(chosen.roomPlace().getId());
+			pickedPlaces.add(chosen.roomPlace());
+			pickedIds.add(chosen.roomPlace().getId());
 			prev = chosen;
 		}
 
-		List<RoomPlace> pickedPlaces = pool.all().stream()
-				.filter(c -> picked.contains(c.roomPlace().getId()))
-				.sorted(Comparator.comparingInt(c -> picked.indexOf(c.roomPlace().getId())))
-				.map(AvailableCandidate::roomPlace)
-				.toList();
-
-		globallyUsedIds.addAll(picked);
+		globallyUsedIds.addAll(pickedIds);
 		return new CourseSelectionResult(pickedPlaces, skipped);
 	}
 

src/main/java/com/hufs/capstone/backend/course/domain/entity/DateCoursePlace.java

@@ -52,6 +52,9 @@ public static DateCoursePlace create(DateCourse dateCourse, RoomPlace roomPlace,
 		if (dateCourse == null || roomPlace == null || sequenceOrder == null) {
 			throw new IllegalArgumentException("DateCoursePlace required values are missing.");
 		}
+		if (sequenceOrder < 0) {
+			throw new IllegalArgumentException("DateCoursePlace required values are missing.");
+		}
 		return new DateCoursePlace(dateCourse, roomPlace, sequenceOrder);
 	}
 }

src/test/java/com/hufs/capstone/backend/course/application/HaversineTest.java

@@ -32,7 +32,7 @@ void approxOneKmBetweenNearbyPoints() {
 	}
 
 	@Test
-	void approxHundredKmBetweenSeoulAndSuwon() {
+	void approxFortyFiveKmBetweenSeoulAndSuwon() {
 		// Seoul to Suwon (~45 km by Haversine)
 		double km = Haversine.km(
 				BigDecimal.valueOf(37.5665),