start method
Called by SmartConnectivityMonitor.initialize.
Implementation
Future<void> start() async {
// Emit cached state immediately for instant UI on launch.
final cached = await _cache.read();
if (cached != null) {
_subject.add(ConnectivityLoaded(cached));
}
// Wire monitor → state.
_monitorSub = _monitorService.stream.listen(
_onResult,
onError: (Object e) {
_subject.add(ConnectivityError(e.toString()));
},
);
// Start the monitor engine.
await _monitorService.start();
}