A way to export slug as meta tag

I don’t think there is a built-in mechanism to write meta tags, no: you have to echo it from a wp_head hook. For example:

function slug_meta_tag()
{
    if ( is_single() ) {
        global $post;
        if ( $post && $post->post_name ) {
            echo '<meta name="slug" content="' . esc_html( $post->post_name ) . '" />';
        }
    }
}
add_action( 'wp_head', 'slug_meta_tag', 10, 0 );

(I’m using the top answer here to get the slug, but there are other approaches there too.)