Markdown export for every docs page

Every documentation page — generated API reference included — can now be copied or downloaded as clean Markdown, ready to paste into an editor, a coding assistant, or your own internal docs.

Each page carries actions to copy its Markdown source or download it as a .md file. Endpoint pages also have a copy button on the method and path, so grabbing just the route doesn't mean selecting text by hand.

Markdown round-trips cleanly where a screenshot or a copy-paste from rendered HTML doesn't: tables stay tables, code blocks stay code blocks, and enum values survive intact.

The site also publishes an llms.txt index, so tooling that understands that convention can discover the full documentation set on its own.