feat(claude-do): Neu angelegter Task soll direkt ausgewählt werden (Detailpan

## Problem
Nach "Neuen Task hinzufügen" (Eingabefeld im Tasks-Header, `Ctrl+N`) wird der Task angelegt und in die
Liste eingefügt, aber **nicht ausgewählt**. Um Beschreibung/Config zu ergänzen, muss man ihn erst
manuell anklicken.

## Ist-Zustand
`src/ClaudeDo.Ui/ViewModels/Islands/TasksIslandViewModel.cs`, `AddAsync()` (ab Zeile ~424):
legt die `TaskEntity` an, speichert über `TaskRepository.AddA

ClaudeDo-Task: 5af6ac9acb4447929e3e550c3c233a25

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

@@ -443,6 +443,7 @@ public sealed partial class TasksIslandViewModel : ViewModelBase, IDisposable
         row.ShowListChip = _currentList?.Kind == ListKind.Virtual;
         Items.Add(row);
         Regroup();
+        SelectedTask = row;
         NewTaskTitle = "";
         UpdateSubtitle();
         TasksChanged?.Invoke(this, EventArgs.Empty);

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

@@ -0,0 +1,76 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Ui.ViewModels.Islands;
+using Microsoft.EntityFrameworkCore;
+
+namespace ClaudeDo.Ui.Tests.ViewModels;
+
+public class TasksIslandAddAndSelectTests : IDisposable
+{
+    private readonly string _dbPath;
+
+    public TasksIslandAddAndSelectTests()
+    {
+        _dbPath = Path.Combine(Path.GetTempPath(), $"claudedo_ui_addselect_{Guid.NewGuid():N}.db");
+        using var ctx = NewContext();
+        ctx.Database.EnsureCreated();
+    }
+
+    public void Dispose()
+    {
+        try { File.Delete(_dbPath); } catch { }
+        try { File.Delete(_dbPath + "-wal"); } catch { }
+        try { File.Delete(_dbPath + "-shm"); } catch { }
+    }
+
+    private ClaudeDoDbContext NewContext()
+    {
+        var opts = new DbContextOptionsBuilder<ClaudeDoDbContext>()
+            .UseSqlite($"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 SeedListAsync()
+    {
+        await using var db = NewContext();
+        db.Lists.Add(new ListEntity { Id = "L1", Name = "Work", CreatedAt = DateTime.UtcNow });
+        await db.SaveChangesAsync();
+    }
+
+    [Fact]
+    public async Task AddAsync_SelectsNewTask()
+    {
+        await SeedListAsync();
+        var vm = new TasksIslandViewModel(new TestDbFactory(NewContext), worker: null);
+        vm.LoadForList(new ListNavItemViewModel { Id = "user:L1", Name = "Work", Kind = ListKind.User });
+        await vm.LoadTask!;
+
+        vm.NewTaskTitle = "My new task";
+        await vm.AddCommand.ExecuteAsync(null);
+
+        Assert.NotNull(vm.SelectedTask);
+        Assert.Equal("My new task", vm.SelectedTask!.Title);
+    }
+
+    [Fact]
+    public async Task AddAsync_EmptyTitle_DoesNotChangeSelection()
+    {
+        await SeedListAsync();
+        var vm = new TasksIslandViewModel(new TestDbFactory(NewContext), worker: null);
+        vm.LoadForList(new ListNavItemViewModel { Id = "user:L1", Name = "Work", Kind = ListKind.User });
+        await vm.LoadTask!;
+
+        vm.NewTaskTitle = "";
+        await vm.AddCommand.ExecuteAsync(null);
+
+        Assert.Null(vm.SelectedTask);
+    }
+}