DiscoverResult contains invalid server_info field

[howardjohn]

Pulling this out from a comment

Is this right? looking at the latest spec https://modelcontextprotocol.io/specification/draft/schema#discoverresult this is not even a field in the type anymore after a late spec change modelcontextprotocol/modelcontextprotocol#3002.

Originally posted by @howardjohn in #1044

[tsarlandie-oai]

Agreed that there is a problem when serializing DiscoverResult responses on a server in modern mode. We should not include serverInfo at the top level, we should save it as a _meta field instead.