fix: preserve Copilot terminal viewport during startup

src/DevSpaces/DevSpaceRegistry.cs

@@ -12,15 +12,6 @@ public static ViewModels.DevSpaces GetOrCreate(ViewModels.Repository repository)
             return GetOrCreateEntry(repository)?.Model;
         }
 
-        public static void PrepareForRepositorySwitch(ViewModels.Repository repository)
-        {
-            if (repository == null || string.IsNullOrEmpty(repository.FullPath))
-                return;
-
-            if (_spaces.TryGetValue(repository.FullPath, out var entry))
-                entry.Model.ActivateDashboard();
-        }
-
         public static ViewModels.DevSpaces Attach(ViewModels.Repository repository, Border host)
         {
             if (repository == null || host == null)

src/DevSpaces/TerminalViewportState.cs

@@ -0,0 +1,51 @@
+using System;
+
+namespace DevBoard.DevSpaces
+{
+    internal sealed class TerminalViewportState
+    {
+        public void Update(int columns, int rows)
+        {
+            if (columns <= 0 || rows <= 0)
+                return;
+
+            lock (_gate)
+            {
+                _columns = columns;
+                _rows = rows;
+                _apply?.Invoke(columns, rows);
+            }
+        }
+
+        public void Attach(Action<int, int> apply)
+        {
+            ArgumentNullException.ThrowIfNull(apply);
+
+            lock (_gate)
+            {
+                _apply = apply;
+                apply(_columns, _rows);
+            }
+        }
+
+        public void Detach()
+        {
+            lock (_gate)
+                _apply = null;
+        }
+
+        public (int Columns, int Rows) Current
+        {
+            get
+            {
+                lock (_gate)
+                    return (_columns, _rows);
+            }
+        }
+
+        private readonly object _gate = new();
+        private Action<int, int> _apply;
+        private int _columns = 80;
+        private int _rows = 25;
+    }
+}

src/DevSpaces/WindowsTerminalDevSpaceSurface.cs

@@ -55,18 +55,20 @@ public async Task StartAsync(DevSpaceLaunchSpec spec)
 
             await _host.WaitForNativeCreatedAsync(_cts.Token).ConfigureAwait(false);
 
+            var viewport = _viewport.Current;
             var options = new PtyOptions
             {
                 Name = spec.Process,
                 App = spec.Process,
                 CommandLine = spec.Arguments,
                 Cwd = spec.WorkingDirectory,
-                Cols = 80,
-                Rows = 25,
+                Cols = viewport.Columns,
+                Rows = viewport.Rows,
             };
 
             _pty = await PtyProvider.SpawnAsync(options, _cts.Token).ConfigureAwait(false);
             _pty.ProcessExited += OnProcessExited;
+            _viewport.Attach(ResizePty);
             _acceptInput = true;
 
             _readerTask = ReadOutputAsync(_cts.Token);
@@ -97,6 +99,7 @@ public void Stop()
             _host.TerminalResized -= OnTerminalResized;
             _host.ScrollChanged -= OnScrollChanged;
             _scrollBar.PropertyChanged -= OnScrollBarPropertyChanged;
+            _viewport.Detach();
 
             var pty = _pty;
             _pty = null;
@@ -208,9 +211,11 @@ private void OnInputGenerated(string text)
 
         private void OnTerminalResized(int cols, int rows)
         {
-            if (cols <= 0 || rows <= 0)
-                return;
+            _viewport.Update(cols, rows);
+        }
 
+        private void ResizePty(int cols, int rows)
+        {
             try
             {
                 _pty?.Resize(cols, rows);
@@ -276,6 +281,7 @@ private void RaiseExited(int exitCode)
         private readonly Views.WindowsTerminalNativeHost _host = new();
         private readonly ScrollBar _scrollBar = new();
         private readonly TerminalTranscriptSink _transcriptSink;
+        private readonly TerminalViewportState _viewport = new();
         private readonly CancellationTokenSource _cts = new();
         private readonly Channel<string> _input = Channel.CreateUnbounded<string>(new UnboundedChannelOptions
         {

tests/DevBoard.Tests/TerminalViewportStateDetachTests.cs

@@ -0,0 +1,20 @@
+using DevBoard.DevSpaces;
+using Xunit;
+
+namespace DevBoard.Tests;
+
+public class TerminalViewportStateDetachTests
+{
+    [Fact]
+    public void Detach_StopsApplyingFutureResizeEvents()
+    {
+        var state = new TerminalViewportState();
+        var calls = 0;
+        state.Attach((_, _) => calls++);
+        state.Detach();
+
+        state.Update(140, 48);
+
+        Assert.Equal(1, calls);
+    }
+}

tests/DevBoard.Tests/TerminalViewportStateTests.cs

@@ -0,0 +1,44 @@
+using DevBoard.DevSpaces;
+using Xunit;
+
+namespace DevBoard.Tests;
+
+public class TerminalViewportStateTests
+{
+    [Fact]
+    public void Attach_ReplaysSizeObservedBeforePtyExists()
+    {
+        var state = new TerminalViewportState();
+        state.Update(132, 44);
+
+        (int Columns, int Rows)? applied = null;
+        state.Attach((columns, rows) => applied = (columns, rows));
+
+        Assert.Equal((132, 44), applied);
+    }
+
+    [Fact]
+    public void Update_AppliesNewSizeAfterPtyIsAttached()
+    {
+        var state = new TerminalViewportState();
+        (int Columns, int Rows)? applied = null;
+        state.Attach((columns, rows) => applied = (columns, rows));
+
+        state.Update(101, 37);
+
+        Assert.Equal((101, 37), applied);
+    }
+
+    [Fact]
+    public void InvalidSize_DoesNotReplaceLastValidViewport()
+    {
+        var state = new TerminalViewportState();
+        state.Update(120, 40);
+        state.Update(0, 0);
+
+        (int Columns, int Rows)? applied = null;
+        state.Attach((columns, rows) => applied = (columns, rows));
+
+        Assert.Equal((120, 40), applied);
+    }
+}