Function api_index 

pub fn api_index(crates: &[String]) -> String

The landing page rustdoc does not write.

rustdoc emits a root index.html only when it has a single root crate to point at; documenting a workspace with --no-deps leaves that root empty, so the book’s /api/ link would land on nothing.

Styled from theme/choir-tokens.css, which the build copies in beside it, so this page and the book are the same colours rather than merely adjacent. It carries no script and no external request, which is the same rule the node’s own pages follow.