Add support for HTTP streamable transport validation

[madorn]

Currently, mcp-validation only supports validating MCP servers that use stdio transport. This limits testing to command-line MCP servers and excludes HTTP-based implementations.

Add support for validating MCP servers that use HTTP streamable transport as defined in the MCP specification.

stdio:
mcp-validate -- python server.py

streamable-http:
mcp-validate --transport http --endpoint http://localhost:3000/mcp

SSE is another transport option but it should be noted that SSE transport became deprecated in 2025-03-26 and streamable-http was introduced.

We should look into bumping use of 2024-11-05 spec in protocol validator to 2025-03-26 to comply with use of http-streamable.

mcp-validation/mcp_validation/validators/protocol.py

Line 78 in dbe77b1

"protocolVersion": "2024-11-05",