updateChatHeadIcon method
Replaces the chathead icon with raw RGBA pixel data.
id identifies which bubble to update. rgbaBytes contains the
pixel data in RGBA order, with dimensions width × height.
On Android the bitmap is created off the main thread; on iOS the chathead is already a Flutter view so this is a no-op.
Implementation
@override
Future<void> updateChatHeadIcon(
String id,
Uint8List rgbaBytes,
int width,
int height,
) async {
lastIconId = id;
lastIconBytes = rgbaBytes;
}