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.

先追蹤 mcp dev 和 mcp run 命令的進入點，並比較它們如何處理高階和低階 Server 類別。閱讀 server/lowlevel/server.py 和現有的 Settings 類別，以了解缺少的 dependencies 欄位。完成的要求是 maintainer 對設計達成共識，並驗證兩個命令都支援低階 Server。