fix(worker,ui): route details-pane task delete through worker to advance blocked parents

Deleting a child from the details pane hard-deleted straight from the UI
process via TaskRepository, bypassing TaskStateService.TryAdvanceParentAsync
entirely. Deleting the last child of a WaitingForChildren parent that way
left it wedged forever. WorkerHub.DeleteTask now mirrors the MCP delete_task
tool (running-task guard, FK-friendly error, advance-parent call), and the
UI goes through it.

TryAdvanceParentAsync also short-circuited when zero children remained,
treating "no children left" as "nothing to evaluate" instead of "all done" -
removed the early return so an empty child list (vacuously) counts as all
terminal.

tests/ClaudeDo.Ui.Tests/StubWorkerClient.cs

@@ -79,6 +79,7 @@ public abstract class StubWorkerClient : IWorkerClient
     public virtual Task<PendingQuestionDto?> GetPendingQuestionAsync(string taskId) => Task.FromResult(PendingQuestion);
     public virtual Task ResetTaskAsync(string taskId) => Task.CompletedTask;
     public virtual Task CancelTaskAsync(string taskId) => Task.CompletedTask;
+    public virtual Task<(bool Ok, string? Error)> DeleteTaskAsync(string taskId) => Task.FromResult<(bool, string?)>((true, null));
     public virtual Task<List<AgentInfo>> GetAgentsAsync() => Task.FromResult(new List<AgentInfo>());
     public virtual Task RefreshAgentsAsync() => Task.CompletedTask;
     public virtual Task<SeedResultDto?> RestoreDefaultAgentsAsync() => Task.FromResult<SeedResultDto?>(null);

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

@@ -0,0 +1,117 @@
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Ui.Services;
+using ClaudeDo.Ui.ViewModels.Islands;
+using Microsoft.EntityFrameworkCore;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Ui.Tests.ViewModels;
+
+public class DetailsIslandDeleteTaskTests : IDisposable
+{
+    private readonly string _dbPath;
+
+    public DetailsIslandDeleteTaskTests()
+    {
+        _dbPath = Path.Combine(Path.GetTempPath(), $"claudedo_delete_task_test_{Guid.NewGuid():N}.db");
+        using var ctx = NewContext();
+        ctx.Database.EnsureCreated();
+    }
+
+    public void Dispose()
+    {
+        try { File.Delete(_dbPath); } catch { }
+        try { File.Delete(_dbPath + "-wal"); } catch { }
+        try { File.Delete(_dbPath + "-shm"); } catch { }
+    }
+
+    private ClaudeDoDbContext NewContext()
+    {
+        var opts = new DbContextOptionsBuilder<ClaudeDoDbContext>()
+            .UseSqlite($"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 sealed class NullServiceProvider : IServiceProvider
+    {
+        public object? GetService(Type serviceType) => null;
+    }
+
+    private sealed class StubNotesApi : ClaudeDo.Ui.Services.Interfaces.INotesApi
+    {
+        public Task<List<DailyNoteDto>> ListAsync(DateOnly day) =>
+            Task.FromResult(new List<DailyNoteDto>());
+        public Task<DailyNoteDto?> AddAsync(DateOnly day, string text) =>
+            Task.FromResult<DailyNoteDto?>(null);
+        public Task UpdateAsync(string id, string text) => Task.CompletedTask;
+        public Task DeleteAsync(string id) => Task.CompletedTask;
+    }
+
+    private sealed class RecordingWorkerClient : StubWorkerClient
+    {
+        public override bool IsConnected => true;
+        public (bool Ok, string? Error) Result { get; set; } = (true, null);
+        public string? DeletedTaskId { get; private set; }
+
+        public override Task<(bool Ok, string? Error)> DeleteTaskAsync(string taskId)
+        {
+            DeletedTaskId = taskId;
+            return Task.FromResult(Result);
+        }
+    }
+
+    private DetailsIslandViewModel BuildVm(RecordingWorkerClient worker)
+    {
+        var factory = new TestDbFactory(NewContext);
+        return new DetailsIslandViewModel(factory, worker, new NullServiceProvider(), new StubNotesApi(), new ClaudeDo.Ui.Services.MergeCoordinator());
+    }
+
+    [Fact]
+    public async Task DeleteTask_Succeeds_RemovesFromListAndClosesDetail()
+    {
+        var worker = new RecordingWorkerClient { Result = (true, null) };
+        var vm = BuildVm(worker);
+        vm.Bind(new TaskRowViewModel { Id = "task-del-1", Status = TaskStatus.Idle });
+
+        TaskRowViewModel? removed = null;
+        vm.DeleteFromList = row => { removed = row; return Task.CompletedTask; };
+        var closed = false;
+        vm.CloseDetail = () => closed = true;
+
+        await vm.DeleteTaskCommand.ExecuteAsync(null);
+
+        Assert.Equal("task-del-1", worker.DeletedTaskId);
+        Assert.Equal("task-del-1", removed?.Id);
+        Assert.True(closed);
+    }
+
+    [Fact]
+    public async Task DeleteTask_WhenTaskHasChildren_SurfacesErrorAndKeepsDetailOpen()
+    {
+        const string fkMessage = "This task has child tasks. Discard the planning session or delete child tasks first.";
+        var worker = new RecordingWorkerClient { Result = (false, fkMessage) };
+        var vm = BuildVm(worker);
+        vm.Bind(new TaskRowViewModel { Id = "task-del-2", Status = TaskStatus.WaitingForChildren });
+
+        var deleteFromListCalled = false;
+        vm.DeleteFromList = _ => { deleteFromListCalled = true; return Task.CompletedTask; };
+        var closed = false;
+        vm.CloseDetail = () => closed = true;
+        string? reportedError = null;
+        vm.ShowErrorAsync = msg => { reportedError = msg; return Task.CompletedTask; };
+
+        await vm.DeleteTaskCommand.ExecuteAsync(null);
+
+        Assert.Equal(fkMessage, reportedError);
+        Assert.False(deleteFromListCalled);
+        Assert.False(closed);
+    }
+}