hardened API decoding against server fields the models did not expect

The Talk room list crashed for a new account because the server omits
lastMessage for rooms without a visible message and the model required it.
Beyond that single field, a review of the Talk models against the OpenAPI
spec of the installed version (23.0.8) found the same crash class in several
places: closed enums over open server values (inCall bitmask, rich-object
types, actor and message types), a deleted parent sent as {id, deleted},
and the autocomplete status arriving as an object.

- json_serializable `checked: true`: decode errors now name class and field
- lists (rooms, messages, participants, autocomplete) decode per entry;
  a malformed entry is skipped and reported via ClientErrorReporter
- unknownEnumValue fallbacks for all response enums of Talk and breakers
- lastMessage nullable; inCall as bitmask; deleted parent placeholder;
  autocomplete status object/string; fixed shareWithDisplayNameUnique key
- GetRoomParams no longer sends null query parameters

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HrepDTL4qDe35TuS29sLW3

lib/storage/chat_background_settings.g.dart

@@ -8,14 +8,23 @@ part of 'chat_background_settings.dart';
 
 ChatBackgroundSettings _$ChatBackgroundSettingsFromJson(
   Map<String, dynamic> json,
-) => ChatBackgroundSettings(
-  type: $enumDecode(_$ChatBackgroundTypeEnumMap, json['type']),
-  fit: $enumDecode(_$ChatBackgroundFitEnumMap, json['fit']),
-  colorValue: (json['colorValue'] as num?)?.toInt(),
-  imageVersion: (json['imageVersion'] as num).toInt(),
-  dim: (json['dim'] as num).toDouble(),
-  blur: (json['blur'] as num).toDouble(),
-);
+) => $checkedCreate('ChatBackgroundSettings', json, ($checkedConvert) {
+  final val = ChatBackgroundSettings(
+    type: $checkedConvert(
+      'type',
+      (v) => $enumDecode(_$ChatBackgroundTypeEnumMap, v),
+    ),
+    fit: $checkedConvert(
+      'fit',
+      (v) => $enumDecode(_$ChatBackgroundFitEnumMap, v),
+    ),
+    colorValue: $checkedConvert('colorValue', (v) => (v as num?)?.toInt()),
+    imageVersion: $checkedConvert('imageVersion', (v) => (v as num).toInt()),
+    dim: $checkedConvert('dim', (v) => (v as num).toDouble()),
+    blur: $checkedConvert('blur', (v) => (v as num).toDouble()),
+  );
+  return val;
+});
 
 Map<String, dynamic> _$ChatBackgroundSettingsToJson(
   ChatBackgroundSettings instance,