Migrate KIT documentation from MDX to MD and remove redundant openAPI folder

[stephanbcbauer]

Summary

Switch all documentation files in the KIT section from .mdx to .md, since advanced MDX features are not needed. Additionally, delete the redundant openAPI folder within the KIT; only the YAML file in the main openAPI folder is required.

Tasks

• Convert all relevant .mdx files in the KIT documentation to .md files
• Ensure all documentation content is preserved and properly rendered
• Delete the openAPI folder within the KIT section
• Move or update references to the YAML specification so that only the main openAPI folder contains it

Motivation

This change simplifies the documentation structure, avoids unnecessary complexity, and removes redundancy by storing the OpenAPI YAML in a single location.

References

was also mentioned in the #1311

@jSchuetz88 FYI