Function set_header_bold 

pub fn set_header_bold<I, T>(table: &mut Table, ctx: &OutputCtx, columns: I)
where
    I: IntoIterator<Item = T>,
    T: Into<String>,

Sets the table header docker/kubectl-style: ALL-CAPS bold cells (bold only when colors are active — otherwise we’d dump raw ANSI escapes into piped output). Callers should pass already-uppercased strings.

Also configures two-space right padding on every column; with the borderless preset that gap is the only thing separating columns.