fix: keep fetch when shadow-DOM prerender retry is 4xx - #277

Bugbot Analysis Progress (1m 39s elapsed)

✅ Gathered PR context (2s)
✅ Completed bug detection (1m 37s)
✅ Posted analysis results (0s)

Final Result: Bugbot completed review - no issues found! ✅

Request ID: serverGenReqId_3d0c7590-55c9-4ead-9fe0-62483fe8d0d5