Agent Markdown and UTF-8 responses

A public Markdown copy of the API docs was added, and responses continue to be served as UTF-8.

The API documentation now has a public Markdown file so a person or a coding agent can read the same limits, endpoints, and examples. Pages and API responses are served as UTF-8. Custom aliases are still ASCII only: letters, numbers, hyphens, and underscores. Broader Unicode aliases are not offered.