Follow-up improvements for #289 and #333

[maeryo]

Motivation and Context

To address feedback from #289 and improve areas that needed enhancement.

How Has This Been Tested?

[x] Unit tests

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)
• Refactoring (non-breaking change which improves code structure)
• Test improvements

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

This is a follow-up PR to #289 and #333.

Changes made:

• Moved regex patterns to static constants: labelPattern and namePattern are now defined in the Client companion object to prevent repeated regex compilation
• Extracted JSON conversion logic: Created a separate JsonConverter utility object to improve code organization and reusability
• Enhanced test coverage: Added comprehensive assertions for meta content validation in ClientMetaParameterTest to verify actual values rather than just absence of exceptions

Note

Once #333 is merged, I will apply the new MockTransport to this PR. Until then, some test failures are expected.
Happy to discuss any suggestions for improvement.