fix(transport): Handle multi-line and concatenated JSON-RPC messages

[mrchypark]

This pull request fixes an issue in the Stdio transport where it incorrectly assumes that each JSON-RPC message arrives on a single line. The previous implementation would parse each line break, leading to Parse error for valid, formatted multi-line JSON inputs.

This change modifies the reader goroutine in mcp/transport.go to:

1. Buffer incoming data from the reader.
2. Intelligently scan the buffer for a complete JSON object by tracking the balance of curly braces ({}), while correctly ignoring braces inside string literals.
3. Only attempt to process a message once a full, valid JSON object has been detected in the buffer.

This new approach ensures that emcee can robustly handle:

• Formatted, multi-line JSON objects.
• Multiple JSON objects sent in a single stream (concatenated).

This significantly improves the usability and robustness of the Stdio transport, making it more resilient to different input formats.

[mattt]

Hi @mrchypark. Thanks so much for contributing this PR.

emcee pre-dates any community implementations of the MCP spec in Go, and this was also my first introduction to the protocol. So there are a bunch of problems like this. I just merged #58, which swaps in the official Go SDK. This is now available in the latest release (v0.6.0).

Can you please give that a try and let me know if you're still seeing this issue?

[mrchypark]

good to me version 0.6.0

thank you!

[mattt]

@mrchypark Awesome. Thanks so much for confirming. I'll go ahead and close this PR.