Fix height of chat boxes

lib/screens/tasks/task_detail_screen.dart

@@ -2026,18 +2026,16 @@ class _TaskDetailScreenState extends ConsumerState<TaskDetailScreen>
             );
           }
 
-          // Mobile: make whole detail screen scrollable and give the
-          // tabbed area a fixed height so it can layout inside the
-          // scrollable column.
-          final mobileTabHeight = MediaQuery.of(context).size.height * 0.72;
-          return SingleChildScrollView(
-            child: Column(
-              children: [
-                detailsCard,
-                const SizedBox(height: 12),
-                SizedBox(height: mobileTabHeight, child: tabbedCard),
-              ],
-            ),
+          // Mobile: avoid two scrollables nested together. detailsCard can
+          // independently scroll and the tabbed card takes whatever space
+          // remains so the chat/activity list always receives gestures and
+          // can never be pushed completely offscreen.
+          return Column(
+            children: [
+              detailsCard,
+              const SizedBox(height: 12),
+              Expanded(child: tabbedCard),
+            ],
           );
         },
       ),