wrapCommand method
Wraps a user-typed line so it runs and is followed by tail (a marker)
as one logical unit. interactive enables terminal-echo handling where the
dialect needs it (POSIX only; pipe-based Windows shells don't echo stdin).
Implementation
@override
String wrapCommand(
String line, {
required bool interactive,
required String tail,
}) {
// `&` runs the marker regardless of the command's exit status.
return '$line & $tail';
}