feat: Add mcp transport protocol

[twishabansal]

In this PR, the MCP protocol does not yet support Auth related functionality such as Authorized Invocations and Authenticated Parameters.

Therefore, the default is still the Toolbox Protocol here.

Note: This PR is currently based on two separate PRs. The protocol is added in #348. This will be updated once the protocol object PR is merged.

[twishabansal]

/gcbrun

[kurtisvg]

At a high level, I'm concerned with the type safety of this approach. Given we have such concrete types defined by MCP, we should be re-implementing those for each version and ensuring requests and responses match them correctly. As is, this method seems difficult to scale as MCP evolves over time.

An example of what this should look like is probably more then like protocol.py is defined here.

[twishabansal]

At a high level, I'm concerned with the type safety of this approach. Given we have such concrete types defined by MCP, we should be re-implementing those for each version and ensuring requests and responses match them correctly. As is, this method seems difficult to scale as MCP evolves over time.

An example of what this should look like is probably more then like protocol.py is defined here.

I have refactored this PR accordingly. Please have a look!