Remove problematic Client.handleMessage call

[ruifigueira]

Client has no handleMessage function, and it was causing a failure in playground AI:

[debug] Error details: {"message":"_a.handleMessage is not a function","stack":"TypeError: _a.handleMessage is not a function\n at transportInstance.onmessage (http://localhost:5173/node_modules/.vite/deps/use-mcp_react.js?v=24c67158:7940:56)\n at _transport.onmessage (http://localhost:5173/node_modules/.vite/deps/use-mcp_react.js?v=24c67158:7240:63)\n at processStream (http://localhost:5173/node_modules/.vite/deps/use-mcp_react.js?v=24c67158:7004:77)","name":"TypeError"}

I detected this issue while I was doing some customizations to playground AI, and I also noticed that the official playgroung AI is failing right now (I didn't investigate to check if it's for the same reason).

To reproduce:

• launch playground AI
• set MCP Server to https://browser.mcp.cloudflare.com/mcp
• click Connect
• the Debug log displays the error above

Motivation and Context

It's causing problems when trying to connect to an MCP server in playground AI.

How Has This Been Tested?

Yes, see above.

Breaking Changes

No.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
  • I didn't run the tests because they don't seem to work in windows due to spawn calls for server setup
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[geelen]

Duplicate of #9 which I'm releasing now. Sorry for the chaos but I'm getting on top of it! 😅