Relocate tests under /test

[KKonstantinov]

Relocate tests under /test, reusable test helpers

Motivation and Context

Tests consolidated under tests allows for reusable helpers between tests and a clearer src folder.

How Has This Been Tested?

Lint, test.

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

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/sdk@1220

commit: 6862f55