chore: Follow up new sliverappbar in chatlist

lib/pages/chat_list/chat_list_header.dart

@@ -19,10 +19,11 @@ class ChatListHeader extends StatelessWidget implements PreferredSizeWidget {
 
     return SliverAppBar(
       floating: true,
-      pinned: FluffyThemes.isColumnMode(context),
-      elevation: 0,
-      scrolledUnderElevation: 0,
-      backgroundColor: Colors.transparent,
+      pinned:
+          FluffyThemes.isColumnMode(context) || selectMode != SelectMode.normal,
+      scrolledUnderElevation: selectMode == SelectMode.normal ? 0 : null,
+      backgroundColor:
+          selectMode == SelectMode.normal ? Colors.transparent : null,
       automaticallyImplyLeading: false,
       leading: selectMode == SelectMode.normal
           ? null
@@ -44,12 +45,6 @@ class ChatListHeader extends StatelessWidget implements PreferredSizeWidget {
                 )
               : SizedBox(
                   height: 44,
-                  child: Material(
-                    elevation:
-                        Theme.of(context).appBarTheme.scrolledUnderElevation ??
-                            4,
-                    shadowColor: Theme.of(context).appBarTheme.shadowColor,
-                    borderRadius: BorderRadius.circular(AppConfig.borderRadius),
                   child: TextField(
                     controller: controller.searchController,
                     textInputAction: TextInputAction.search,
@@ -67,13 +62,11 @@ class ChatListHeader extends StatelessWidget implements PreferredSizeWidget {
                               tooltip: L10n.of(context)!.cancel,
                               icon: const Icon(Icons.close_outlined),
                               onPressed: controller.cancelSearch,
-                                color:
-                                    Theme.of(context).colorScheme.onBackground,
+                              color: Theme.of(context).colorScheme.onBackground,
                             )
                           : Icon(
                               Icons.search_outlined,
-                                color:
-                                    Theme.of(context).colorScheme.onBackground,
+                              color: Theme.of(context).colorScheme.onBackground,
                             ),
                       suffixIcon: controller.isSearchMode
                           ? controller.isSearching
@@ -110,7 +103,6 @@ class ChatListHeader extends StatelessWidget implements PreferredSizeWidget {
                     ),
                   ),
                 ),
-                ),
       actions: selectMode == SelectMode.share
           ? [
               Padding(