Function transform_links 

pub fn transform_links(
    html: &str,
    current_path: &Path,
    path_to_filename: &HashMap<PathBuf, String>,
    workspace_dir: &Path,
    dest_filename: &str,
) -> String

Rewrite internal .md hyperlinks in rendered HTML to their published .html destinations, resolving relative/workspace-root paths via the path_to_filename map. External links, anchors, and non-.md hrefs are left untouched.

The lookup key is sanitized the same way path_to_filename’s keys are (see sanitize_rel_path), so a link like First post!.md resolves to the stored First post.html instead of a fabricated First post!.html.

A link whose target is not in this render set (excluded by audience visibility, or simply missing) is stripped: the <a> becomes a <span class="unpublished-link"> that keeps the link text but isn’t clickable, so the page never points at something that 404s.

Everything that is not a document link — an image, a PDF, an HTML attachment’s island <iframe> — is then put through rebase_root_absolute, because a vault writes those paths from the vault root (/img/photo.png, prov’s path_style: root) and a site is not always served from a domain root.