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/api/marianumconnect/queries/user_search/user_search_response.g.dart

@@ -7,13 +7,16 @@ part of 'user_search_response.dart';
 // **************************************************************************
 
 McUserSearchResult _$McUserSearchResultFromJson(Map<String, dynamic> json) =>
-    McUserSearchResult(
-      username: json['username'] as String,
-      firstName: json['firstName'] as String,
-      lastName: json['lastName'] as String,
-      userType: json['userType'] as String,
-      className: json['className'] as String?,
-    );
+    $checkedCreate('McUserSearchResult', json, ($checkedConvert) {
+      final val = McUserSearchResult(
+        username: $checkedConvert('username', (v) => v as String),
+        firstName: $checkedConvert('firstName', (v) => v as String),
+        lastName: $checkedConvert('lastName', (v) => v as String),
+        userType: $checkedConvert('userType', (v) => v as String),
+        className: $checkedConvert('className', (v) => v as String?),
+      );
+      return val;
+    });
 
 Map<String, dynamic> _$McUserSearchResultToJson(McUserSearchResult instance) =>
     <String, dynamic>{
@@ -25,14 +28,25 @@ Map<String, dynamic> _$McUserSearchResultToJson(McUserSearchResult instance) =>
     };
 
 UserSearchResponse _$UserSearchResponseFromJson(Map<String, dynamic> json) =>
-    UserSearchResponse(
-        result: (json['result'] as List<dynamic>)
-            .map((e) => McUserSearchResult.fromJson(e as Map<String, dynamic>))
-            .toList(),
-      )
-      ..headers = (json['headers'] as Map<String, dynamic>?)?.map(
-        (k, e) => MapEntry(k, e as String),
+    $checkedCreate('UserSearchResponse', json, ($checkedConvert) {
+      final val = UserSearchResponse(
+        result: $checkedConvert(
+          'result',
+          (v) => (v as List<dynamic>)
+              .map(
+                (e) => McUserSearchResult.fromJson(e as Map<String, dynamic>),
+              )
+              .toList(),
+        ),
       );
+      $checkedConvert(
+        'headers',
+        (v) => val.headers = (v as Map<String, dynamic>?)?.map(
+          (k, e) => MapEntry(k, e as String),
+        ),
+      );
+      return val;
+    });
 
 Map<String, dynamic> _$UserSearchResponseToJson(UserSearchResponse instance) =>
     <String, dynamic>{