fix: parse nested image generation tasks

services/api/app/services/design_pipeline.py

@@ -16,7 +16,7 @@ from app.domain.models import (
     StructureAnalysis,
     StyleDirection,
 )
-from app.integrations.openai_compatible import OpenAICompatibleGateway
+from app.integrations.openai_compatible import OpenAICompatibleGateway, safe_response_diagnostic
 
 
 def crop_plan_preview(preview: bytes, region: PlanRegion | None) -> bytes:
@@ -302,7 +302,8 @@ async def generated_image_bytes(payload: dict[str, Any]) -> tuple[bytes, str]:
         mime = header.split(";", 1)[0].replace("data:", "")
         return base64.b64decode(encoded), mime
     if not url:
-        raise ValueError("生图模型返回了成功响应，但没有图片地址或图片数据。")
+        diagnostic = json.dumps(safe_response_diagnostic(payload), ensure_ascii=False)
+        raise ValueError(f"平台返回体中没有可识别的图片结果。脱敏诊断：{diagnostic}")
     async with httpx.AsyncClient(timeout=90, follow_redirects=True) as client:
         response = await client.get(url)
         response.raise_for_status()