Enhance device management and model handling in SnapForm

- Updated frame extraction logic to allow for single frame extraction.
- Integrated model readiness checks for BEN2 and DA3 models in relevant operators.
- Added directory name attribute to model specifications for better organization.
- Improved device selection logic for production and debug tasks.
- Refactored preferences to expose device settings and ensure they reflect available hardware.
- Enhanced runtime device detection and management, including support for CUDA and MPS.
- Updated tests to cover new device management features and model directory handling.
- Removed deprecated download model tests to streamline codebase.

README.md

@@ -18,8 +18,8 @@ SnapForm 是一个 Blender 扩展，可以把一张照片、一段视频或一
 - Linux：`SnapForm.v0.10.10.linux-x64.zip`
 2. 打开 Blender，进入 `Preferences > Extensions`
 3. 点击 `Install from Disk`，选择下载的压缩包
-4. 在扩展偏好设置中确认 `uv` 路径与 Torch 后端（保持默认即可）；如果下载经常超时，
-   可以在 `PyPI Index` 里填一个国内镜像，例如 `https://pypi.tuna.tsinghua.edu.cn/simple`
+4. 在扩展偏好设置中确认 Storage Root 与 Device（保持默认即可）；Device 默认取本机
+   最快的 CUDA/MPS，否则 CPU。下载超时会自动重试国内镜像，无需手动配置
 5. 打开 3D 视图右侧的 `SnapForm` 面板，点击 `Install Runtime`
 
 DA3、BEN2 源码包和 uv 已内置在扩展里，安装时直接从本地解包，不需要访问 GitHub。首次使用仍会自动