fix(images): 兼容 OpenAI 多图编辑 multipart

- 将 OpenAI images/edits 请求构造成 multipart/form-data
- 在运行时安全转存 URL 图片为 data URL 后提交二进制文件
- 覆盖多图字段、真实上游模型名和内部元数据过滤测试

apps/api/internal/runner/request_assets.go

@@ -160,6 +160,9 @@ func (s *Service) hydrateProviderRequestAssetString(ctx context.Context, value s
 		return value, nil
 	}
 	style, ok := requestAssetCapabilityHydrationForMedia("image", candidate, raw, "")
+	if !ok && openAIImageEditRequiresMultipartBytes(candidate) {
+		style, ok = requestAssetHydrateDataURL, true
+	}
 	if !ok {
 		return value, nil
 	}
@@ -320,6 +323,9 @@ func requestAssetHydrationForField(path []string, asset store.RequestAsset, cand
 		if style, ok := requestAssetCapabilityHydrationForMedia("image", candidate, asset.URL, asset.StorageProvider); ok {
 			return style
 		}
+		if openAIImageEditRequiresMultipartBytes(candidate) {
+			return requestAssetHydrateDataURL
+		}
 	}
 	if mediaURLFieldNeedsHydration(path) {
 		if style := configuredRequestAssetMediaURLHydration(candidate, requestAssetMediaURLKind(path)); style != "" {
@@ -332,6 +338,11 @@ func requestAssetHydrationForField(path []string, asset store.RequestAsset, cand
 	return requestAssetHydrateURL
 }
 
+func openAIImageEditRequiresMultipartBytes(candidate store.RuntimeModelCandidate) bool {
+	return normalizeProviderKey(candidate.Provider) == "openai" &&
+		strings.TrimSpace(candidate.ModelType) == "image_edit"
+}
+
 func requestAssetMediaKindForHydration(path []string, asset store.RequestAsset) string {
 	if mediaURLFieldNeedsHydration(path) {
 		return requestAssetMediaURLKind(path)