Function sanitize_roxygen_links 

fn sanitize_roxygen_links(s: &str) -> String

Neutralize rustdoc intra-doc link syntax so prose is valid roxygen2 markdown.

rustdoc [Foo] / [Foo] / [text][target] are intra-doc links resolved against Rust items by cargo doc. roxygen2 (markdown on) reads the same [...] as an R \link{} to a help topic, which can’t resolve. We strip the link brackets down to the visible text (keeping any `code` span), while leaving genuine markdown links [text](url) — recognized by the ]( that follows — untouched.