Fix adaptive layout: respond to resize via Bounds observable and MeasureOverride

Added BoundsProperty observer and MeasureOverride to detect size
changes from foldable device fold/unfold and rotation. The previous
OnSizeChanged alone was not sufficient on Android.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: sharpninja

src/RequestTracker.Android/Views/AdaptiveMainView.axaml

@@ -1,14 +1,15 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:vm="using:RequestTracker.Core.ViewModels"
-             xmlns:views="using:RequestTracker.Android.Views"
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
              mc:Ignorable="d"
              x:Class="RequestTracker.Android.Views.AdaptiveMainView"
-             x:DataType="vm:MainWindowViewModel">
+             x:DataType="vm:MainWindowViewModel"
+             HorizontalAlignment="Stretch"
+             VerticalAlignment="Stretch">
 
-    <Panel x:Name="HostPanel">
-        <!-- Content is set dynamically in code-behind based on available width -->
-    </Panel>
+    <Panel x:Name="HostPanel"
+           HorizontalAlignment="Stretch"
+           VerticalAlignment="Stretch"/>
 </UserControl>

src/RequestTracker.Android/Views/AdaptiveMainView.axaml.cs

@@ -1,6 +1,7 @@
 using System;
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Layout;
 using Avalonia.Markup.Xaml;
 
 namespace RequestTracker.Android.Views;
@@ -12,7 +13,7 @@ namespace RequestTracker.Android.Views;
 public partial class AdaptiveMainView : UserControl
 {
     private const double TabletWidthThreshold = 600;
-    private bool _isTabletLayout;
+    private bool? _isTabletLayout;
     private Control? _currentView;
     private Panel? _hostPanel;
 
@@ -25,20 +26,40 @@ public AdaptiveMainView()
     protected override void OnSizeChanged(SizeChangedEventArgs e)
     {
         base.OnSizeChanged(e);
-        UpdateLayout(e.NewSize.Width);
+        EvaluateLayout();
     }
 
     protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
     {
         base.OnAttachedToVisualTree(e);
-        UpdateLayout(Bounds.Width);
+        // Also listen to Bounds property changes for Android config changes
+        this.GetObservable(BoundsProperty).Subscribe(new BoundsObserver(this));
+        EvaluateLayout();
     }
 
-    private void UpdateLayout(double availableWidth)
+    private sealed class BoundsObserver : IObserver<Rect>
     {
-        bool shouldBeTablet = availableWidth >= TabletWidthThreshold;
+        private readonly AdaptiveMainView _owner;
+        public BoundsObserver(AdaptiveMainView owner) => _owner = owner;
+        public void OnNext(Rect value) => _owner.EvaluateLayout();
+        public void OnError(Exception error) { }
+        public void OnCompleted() { }
+    }
+
+    protected override Size MeasureOverride(Size availableSize)
+    {
+        EvaluateLayout(availableSize.Width);
+        return base.MeasureOverride(availableSize);
+    }
+
+    private void EvaluateLayout(double? widthOverride = null)
+    {
+        double width = widthOverride ?? Bounds.Width;
+        if (width <= 0) return;
+
+        bool shouldBeTablet = width >= TabletWidthThreshold;
 
-        if (_currentView != null && shouldBeTablet == _isTabletLayout)
+        if (_isTabletLayout.HasValue && shouldBeTablet == _isTabletLayout.Value)
             return;
 
         _isTabletLayout = shouldBeTablet;