Warning: texture-load smoke test only. Some assets use default/grid/fallback textures and are not visually faithful to the original GRScenes USD materials.
随机抽样 12 个 GRScenes 资产，检查 glTF 是否能加载 texture image、material 和 projected TEXCOORD_0。注意：这不是 source-faithful 纹理验收；原转换链丢失 UV/material binding，部分样本会有明显贴图错配。
Warning: texture-load smoke test only. Some assets use default/grid/fallback textures and are not visually faithful to the original GRScenes USD materials.