fixTd3Line1 static method
Implementation
static String fixTd3Line1(String line1) {
if (line1.isEmpty) return line1;
final up = line1.toUpperCase();
final padded = up.length >= _td3Total
? up.substring(0, _td3Total)
: up.padRight(_td3Total, '<');
final docCode = padded.substring(0, 2); // e.g. "P<"
final issuer = padded.substring(2, 5); // e.g. "CAN"
final nameRaw = padded.substring(5); // cols 6–44 (39 chars)
final fixedName = _fixNameField(nameRaw, width: _nameWidth);
return '$docCode$issuer$fixedName';
}