Explain MethodChannels and communicating with native code.

MethodChannels allow asynchronous communication between Dart and platform-specific native code (Kotlin/Swift).

Messages are serialized into a standard format, passed across the platform boundary, and processed asynchronously. You invoke a method on the Dart side, the native side receives the method name and arguments, executes native APIs (like Bluetooth or Camera), and returns a result back to Dart.