maxLineWidth function
Returns the maximum display width across all lines in s.
The input is treated as newline-separated rows; width resets after each newline. This matches how layout code interprets terminal cell widths.
Implementation
int maxLineWidth(String s) {
final normalized = s.replaceAll('\r\n', '\n');
var maxWidth = 0;
for (final line in normalized.split('\n')) {
final w = stringWidth(line);
if (w > maxWidth) maxWidth = w;
}
return maxWidth;
}