fix hang caused by StreamableHttpClientTransport (#226)

[AdrianMiska]

Re-throw exceptions in StreamableHttpClientTransport so Protocol doesn't hang indefinitely.

Motivation and Context

Fixes the issue described in #226

How Has This Been Tested?

I've verified that my test case reproduces the error without my fix, and verified with breakpoints that the hang occurred where I described it.

Breaking Changes

None

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 have added appropriate error handling
• I have added or updated documentation as needed

Additional context

I am unsure about the dispatcher I used for the real-time timeout here. I could not get the test to work otherwise, as kotlinx.coroutines.test was always tripping my timeout, with or without the fix. This is seemingly unrelated to the test case though, as removing my timeout results in the timeout in Protocol being tripped, even though that's not the point of the indefinite hang.