settings: make option immutable

packages/settings/lib/src/options/option.dart

@@ -2,12 +2,14 @@ part of '../../settings.dart';
 
 class OptionDisableException implements Exception {}
 
+@immutable
 abstract class Option<T> {
   Option({
     required this.storage,
     required this.key,
     required this.label,
     required this.defaultValue,
+    required this.stream,
     this.category,
     final BehaviorSubject<bool>? enabled,
   }) : enabled = enabled ?? BehaviorSubject<bool>.seeded(true);
@@ -18,8 +20,8 @@ abstract class Option<T> {
   final T defaultValue;
   final OptionsCategory? category;
   final BehaviorSubject<bool> enabled;
+  final BehaviorSubject<T> stream;
 
-  late BehaviorSubject<T> stream;
   T get value {
     if (hasValue) {
       return stream.value;

packages/settings/lib/src/options/select_option.dart

@@ -9,8 +9,7 @@ class SelectOption<T> extends Option<T> {
     required this.values,
     super.category,
     super.enabled,
-  }) {
-    stream = BehaviorSubject();
+  }) : super(stream: BehaviorSubject()) {
     unawaited(
       values.first.then((final vs) async {
         final valueStr = storage.getString(key);

packages/settings/lib/src/options/toggle_option.dart

@@ -8,9 +8,7 @@ class ToggleOption extends Option<bool> {
     required super.defaultValue,
     super.category,
     super.enabled,
-  }) {
-    stream = BehaviorSubject.seeded(storage.getBool(key) ?? defaultValue);
-  }
+  }) : super(stream: BehaviorSubject.seeded(storage.getBool(key) ?? defaultValue));
 
   @override
   Future set(final bool value) {