profileForDriverId function
Look up a profile by driverId. Returns null when no static
profile maps to that driver - the POS may still attempt a generic
flow against the raw ReaderDevice fields.
Implementation
ReaderProfile? profileForDriverId(String driverId) {
for (final p in knownReaderProfiles) {
if (p.driverId == driverId) return p;
}
return null;
}