Function render_warning 

pub fn render_warning(msg: &str) -> String

Render the themed Warning line for msg: the label right-aligned in the gutter (bold-yellow, no colon) at the enclosing section’s header indent ([label_indent]), so it reads as a peer of the section verbs and its message aligns with theirs. The single source of truth for the warning palette and label, shared by StageLogger::warn and the CLI’s tracing formatter so a library-side warn! looks identical to a logger warn (one output authority).