slug = {
if (providedslug.startsWith("/")) return providedslug.substr(1);
if (/^[0-9a-f]{16}$/.test(providedslug)) return `d/${providedslug}`;
if (providedslug.startsWith("https://observablehq.com/"))
return providedslug.replace("https://observablehq.com/", "");
return providedslug;
}