Support downloading offline package of plugins

### Self Checks

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### 1. Is this request related to a challenge you're experiencing? Tell me about your story.

Support downloading offline packages of plugins.
Many production environments do not support networking, making it impossible to install plug-in packages (with dependencies) at present.
I hope to add support for downloading plugin packages with complete dependencies, so that plugins can be installed and used within the industry in an internet-free environment.

支持下载插件离线包。
很多生产环境不支持联网，无法现在插件包（带有依赖的）。
希望新增支持下载带有完整依赖的插件包，这样就可以在无互联网环境下业内安装和使用插件。

### 2. Additional context or comments

_No response_

### 3. Can you help us with this feature?

- [x] I am interested in contributing to this feature.

No files, tests, or entry points are identified. First trace the existing plugin installation and dependency handling, then clarify the offline package format and supported dependency scope; done means a package can be downloaded with complete dependencies and installed in an environment without network access.

Written by the indexing model from the issue text.