/// Extract brief primer text (title + first section only).
pub(super) fn extract_brief(primer: &str) -> String {
let mut result = String::new();
let mut heading_count = 0;
for line in primer.lines() {
if line.starts_with("## ") {
heading_count += 1;
if heading_count > 1 {
break;
}
}
result.push_str(line);
result.push('\n');
}
result.trim_end().to_string()
}