fix(ui): clear task selection when switching lists

Switching lists rebuilt Tasks.Items from scratch but left SelectedTask pointing
at a row from the previous list, so the detail pane kept showing that task even
though it is not in the visible list. Drop the selection when the list actually
changes; a reload of the same list (worker refresh, reconnect) keeps it so a
live update never yanks the detail pane away.

src/ClaudeDo.Ui/ViewModels/Islands/TasksIslandViewModel.cs

@@ -231,6 +231,12 @@ public sealed partial class TasksIslandViewModel : ViewModelBase, IDisposable
         _loadCts = new CancellationTokenSource();
         var ct = _loadCts.Token;
 
+        // Items is rebuilt from scratch below, so a selection carried over from the previous list
+        // would leave the detail pane bound to a task the visible list no longer contains. Only a
+        // *different* list drops it — a reload of the same list (worker refresh, reconnect) keeps
+        // the selection so a live update never yanks the detail pane away.
+        var listChanged = !string.Equals(_currentList?.Id, list?.Id, StringComparison.Ordinal);
+
         if (_currentList is not null)
             _currentList.PropertyChanged -= OnCurrentListPropertyChanged;
         _currentList = list;
@@ -246,6 +252,7 @@ public sealed partial class TasksIslandViewModel : ViewModelBase, IDisposable
         HasCompleted  = false;
         ShowOpenLabel = false;
         ShowNotesRow  = false;
+        if (listChanged) SelectedTask = null;
         if (list is null) { IsLetClaudeVisible = false; LoadTask = Task.CompletedTask; return; }
 
         HeaderTitle = list.Name;

tests/ClaudeDo.Ui.Tests/ViewModels/TasksIslandListSwitchSelectionTests.cs

@@ -0,0 +1,112 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Ui.ViewModels.Islands;
+using Microsoft.EntityFrameworkCore;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Ui.Tests.ViewModels;
+
+// Switching lists must drop the previous list's selection; reloading the SAME list (worker
+// refresh / reconnect) must keep it, so a live update never yanks the detail pane away.
+public class TasksIslandListSwitchSelectionTests : IDisposable
+{
+    private readonly string _dbPath;
+
+    public TasksIslandListSwitchSelectionTests()
+    {
+        _dbPath = Path.Combine(Path.GetTempPath(), $"claudedo_ui_listswitch_{Guid.NewGuid():N}.db");
+        using var ctx = NewContext();
+        ctx.Database.EnsureCreated();
+    }
+
+    public void Dispose()
+    {
+        try { File.Delete(_dbPath); } catch { }
+        try { File.Delete(_dbPath + "-wal"); } catch { }
+        try { File.Delete(_dbPath + "-shm"); } catch { }
+    }
+
+    private ClaudeDoDbContext NewContext()
+    {
+        var opts = new DbContextOptionsBuilder<ClaudeDoDbContext>()
+            .UseSqlite($"Data Source={_dbPath}")
+            .Options;
+        return new ClaudeDoDbContext(opts);
+    }
+
+    private sealed class TestDbFactory : IDbContextFactory<ClaudeDoDbContext>
+    {
+        private readonly Func<ClaudeDoDbContext> _create;
+        public TestDbFactory(Func<ClaudeDoDbContext> create) => _create = create;
+        public ClaudeDoDbContext CreateDbContext() => _create();
+    }
+
+    private async Task SeedTwoListsAsync()
+    {
+        await using var db = NewContext();
+        db.Lists.Add(new ListEntity { Id = "L1", Name = "Work", CreatedAt = DateTime.UtcNow });
+        db.Lists.Add(new ListEntity { Id = "L2", Name = "Home", CreatedAt = DateTime.UtcNow });
+        db.Tasks.Add(new TaskEntity
+        {
+            Id = "T1", ListId = "L1", Title = "Task one",
+            Status = TaskStatus.Idle, CreatedAt = DateTime.UtcNow, SortOrder = 0,
+        });
+        db.Tasks.Add(new TaskEntity
+        {
+            Id = "T2", ListId = "L2", Title = "Task two",
+            Status = TaskStatus.Idle, CreatedAt = DateTime.UtcNow, SortOrder = 0,
+        });
+        await db.SaveChangesAsync();
+    }
+
+    private static ListNavItemViewModel Nav(string listId, string name) =>
+        new() { Id = $"user:{listId}", Name = name, Kind = ListKind.User };
+
+    [Fact]
+    public async Task LoadForList_OtherList_ClearsSelectedTask_AndRaisesSelectionChanged()
+    {
+        await SeedTwoListsAsync();
+        var vm = new TasksIslandViewModel(new TestDbFactory(NewContext), worker: null);
+
+        vm.LoadForList(Nav("L1", "Work"));
+        Assert.True(await vm.SelectByIdAsync("T1"));
+
+        var selectionChanges = 0;
+        vm.SelectionChanged += (_, _) => selectionChanges++;
+
+        vm.LoadForList(Nav("L2", "Home"));
+        if (vm.LoadTask is { } load) await load;
+
+        Assert.Null(vm.SelectedTask);
+        Assert.Equal(1, selectionChanges);
+    }
+
+    [Fact]
+    public async Task LoadForList_NullList_ClearsSelectedTask()
+    {
+        await SeedTwoListsAsync();
+        var vm = new TasksIslandViewModel(new TestDbFactory(NewContext), worker: null);
+
+        vm.LoadForList(Nav("L1", "Work"));
+        Assert.True(await vm.SelectByIdAsync("T1"));
+
+        vm.LoadForList(null);
+
+        Assert.Null(vm.SelectedTask);
+    }
+
+    [Fact]
+    public async Task LoadForList_SameList_KeepsSelectedTask()
+    {
+        await SeedTwoListsAsync();
+        var vm = new TasksIslandViewModel(new TestDbFactory(NewContext), worker: null);
+
+        vm.LoadForList(Nav("L1", "Work"));
+        Assert.True(await vm.SelectByIdAsync("T1"));
+
+        vm.LoadForList(Nav("L1", "Work"));
+        if (vm.LoadTask is { } load) await load;
+
+        Assert.Equal("T1", vm.SelectedTask?.Id);
+    }
+}