fix: Replace non-standard enumNames with standard oneOf in EnumSchema

[jake-danton]

enumNames is not standard. It's use is keeping this project from updating to ajv v8, which keeps this library from running in some JS runtimes (example #689 ).

Motivation and Context

enumNames is not standard. Its use is keeping this project from updating to ajv v8, which keeps this library from running in some JS runtimes (example #689 ).

Note: requires this schema PR to go through first

How Has This Been Tested?

Ran npm test and used in local development

Breaking Changes

Will require users to update to the standard oneOf where using enumNames.

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