fix: 매니페스트 로드 실패 시 로컬 자산으로 안전하게 대체되지 않는 버그 수정

- normalizeMediaManifest에서 빈 데이터 수신 시 DEFAULT_MEDIA_MANIFEST를 활용하도록 수정
- 매니페스트 로드 실패 시 상세 정보(URL, 상태 코드)를 에러 메시지에 포함
- useMediaCatalog에서 fetch 에러 발생 시 명시적으로 로컬 기반 매니페스트를 적용하도록 보강

src/entities/media/api/mediaManifestApi.ts

@@ -36,6 +36,7 @@ export const mediaManifestApi = {
       return DEFAULT_MEDIA_MANIFEST;
     }
 
+    try {
       const response = await fetch(MEDIA_MANIFEST_URL, {
         method: 'GET',
         cache: MEDIA_MANIFEST_FETCH_CACHE,
@@ -43,10 +44,18 @@ export const mediaManifestApi = {
       });
 
       if (!response.ok) {
-      throw new Error(copy.media.manifestLoadFailed);
+        throw new Error(`${copy.media.manifestLoadFailed} (${response.status} at ${MEDIA_MANIFEST_URL})`);
       }
 
       const payload = (await response.json()) as Partial<MediaManifest>;
       return normalizeMediaManifest(payload);
+    } catch (error) {
+      if (error instanceof Error && error.name === 'AbortError') {
+        throw error;
+      }
+      throw new Error(
+        `${copy.media.manifestLoadFailed}: ${error instanceof Error ? error.message : String(error)} (URL: ${MEDIA_MANIFEST_URL})`
+      );
+    }
   },
 };

src/entities/media/model/resolveMediaAsset.ts

@@ -99,18 +99,18 @@ const mergeSoundAssets = (manifest: MediaManifest) => {
 };
 
 export const normalizeMediaManifest = (manifest: Partial<MediaManifest> | null | undefined): MediaManifest => {
-  const mergedManifest: MediaManifest = {
+  const baseManifest: MediaManifest = {
     version: manifest?.version ?? DEFAULT_MEDIA_MANIFEST.version,
     updatedAt: manifest?.updatedAt ?? DEFAULT_MEDIA_MANIFEST.updatedAt,
     cdnBaseUrl: manifest?.cdnBaseUrl ?? DEFAULT_MEDIA_MANIFEST.cdnBaseUrl,
-    scenes: manifest?.scenes ?? [],
-    sounds: manifest?.sounds ?? [],
+    scenes: manifest?.scenes ?? DEFAULT_MEDIA_MANIFEST.scenes,
+    sounds: manifest?.sounds ?? DEFAULT_MEDIA_MANIFEST.sounds,
   };
 
   return {
-    ...mergedManifest,
-    scenes: mergeSceneAssets(mergedManifest),
-    sounds: mergeSoundAssets(mergedManifest),
+    ...baseManifest,
+    scenes: mergeSceneAssets(baseManifest),
+    sounds: mergeSoundAssets(baseManifest),
   };
 };
 

src/entities/media/model/useMediaCatalog.ts

@@ -40,10 +40,18 @@ const readMediaManifest = async (signal?: AbortSignal): Promise<MediaCatalogLoad
         };
       })
       .catch((error) => {
-        const nextError = error instanceof Error ? error.message : null;
+        // Only return abort errors up the chain if we're not using fallback
+        if (error instanceof Error && error.name === 'AbortError') {
+          throw error;
+        }
+
+        const nextError = error instanceof Error ? error.message : String(error);
+
+        // Explicitly use normalize with null to get a pure fallback manifest
+        const fallbackManifest = normalizeMediaManifest(null);
 
         return {
-          manifest: manifestCache,
+          manifest: fallbackManifest,
           error: nextError,
           usedFallbackManifest: true,
         };