Add group to tools

Hello, I would like to add a group request endpoint, and mark which group it belongs to when registering tools. When using the SSE endpoint, describe the group in the path or parameters. When the client pulls the tool list, it returns the tools of the specified group (if no group is specified, all are returned).

I expect to solve the problem:

1 When a server has many tools, I don't want to use multiple endpoints to group these tools, which is simpler when used in a framework like Spring.
2 Configure different groups to express different agents by obtaining different tool lists.

Note: Alternatively, add a group by interface to handle the group names passed by the SSE endpoint. This interface receives the group name and tools list context, and returns the tools list corresponding to the group name.

首先跟踪现有的 SSE 端点、工具注册流程和工具列表响应。在决定采用端点变更还是分组接口之前，先检查当前如何处理请求参数和已注册工具。完成标准是：服务器可以按组注册工具，通过 SSE 请求一个组，并在未指定组时接收该组或所有工具。