Low-level Server support for mcp dev and mcp run command

Currently the mcp dev and mcp run command does not support the low-level Server class. I think it's a better developer experience if we support both classes for these 2 commands, assuming there's no inherent reason for not doing so.

I'm interested in adding support for the low-level Server to both mcp dev and mcp run and I would like seek the maintainer's guidance on this. It looks like the only thing missing is the dependencies field, which is pulled from the Settings class and does not exist in the low-level Server. I'm thinking about adding a similar Settings class to server/lowlevel/server.py and thus introducing the dependencies field. The downside is more complexity in server/lowlevel/server.py which I'm not sure if it's acceptable to the maintainers and falls in line with the long term roadmap for the code base.

Please advise. Thanks.

首先跟踪 mcp dev 和 mcp run 命令的入口点，并比较它们如何处理高层和低层 Server 类。阅读 server/lowlevel/server.py 和现有的 Settings 类，以了解缺失的 dependencies 字段。完成的要求是 maintainer 就设计达成一致，并验证两个命令都支持低层 Server。