Function render_reference_markdown 

pub fn render_reference_markdown() -> String

Render the full intrinsics reference page as markdown.

The output is a self-contained page with a quick-reference table, followed by per-category detail sections listing each intrinsic’s name, summary, description, runtime binding (if any), preview gate (if any), unchecked requirement (if any), and examples.

This function is the source of truth for the checked-in reference page; make check-intrinsic-docs runs it and fails CI if the committed file differs from the generated output.