TF-3924 Thread Detail Reduce middle state when metadata loading

lib/features/thread_detail/presentation/extension/handle_get_email_ids_by_thread_id_success.dart

@@ -1,3 +1,7 @@
+// ignore_for_file: invalid_use_of_protected_member
+
+import 'package:jmap_dart_client/jmap/mail/email/email.dart';
+import 'package:model/email/presentation_email.dart';
 import 'package:tmail_ui_user/features/thread_detail/domain/state/get_thread_by_id_state.dart';
 import 'package:tmail_ui_user/features/thread_detail/presentation/thread_detail_controller.dart';
 
@@ -32,15 +36,30 @@ extension HandleGetEmailIdsByThreadIdSuccess on ThreadDetailController {
 
     final selectedEmail = mailboxDashBoardController.selectedEmail.value;
     final selectedEmailId = selectedEmail?.id;
-    emailIdsPresentation.value = {
-      for (final id in allEmailIds)
-        id: id == selectedEmailId
-            ? emailIdsPresentation[id] ?? selectedEmail
-            : null,
-    };
+    final originalMap = Map.from(emailIdsPresentation.value);
+    _assignNewThreadEmailIdsWithoutRebuildingTheUI(
+      allEmailIds,
+      selectedEmailId,
+      originalMap,
+      selectedEmail,
+    );
     if ((isThreadDetailEnabled && success is! PreloadEmailIdsInThreadSuccess) ||
         (!isThreadDetailEnabled && success is PreloadEmailIdsInThreadSuccess)) {
       emailsInThreadDetailInfo.value = allEmailsInThreadDetailInfo;
     }
   }
+
+  void _assignNewThreadEmailIdsWithoutRebuildingTheUI(
+    List<EmailId> allEmailIds,
+    EmailId? selectedEmailId,
+    Map<dynamic, dynamic> originalMap,
+    PresentationEmail? selectedEmail,
+  ) {
+    emailIdsPresentation.value..clear()..addAll({
+      for (final id in allEmailIds)
+        id: id == selectedEmailId
+            ? originalMap[id] ?? selectedEmail
+            : null,
+    });
+  }
 }