feat(mcp): allow Done via update_task_status with worktree guard

External tasks finished outside a ClaudeDo run had no way to close out
their tracking task; update_task_status now permits Done alongside
Idle/Queued/Cancelled, refusing it when the task has an active
worktree so review_task stays the only path that merges.

tests/ClaudeDo.Worker.Tests/External/BatchMcpToolsTests.cs

@@ -189,6 +189,22 @@ public sealed class BatchMcpToolsTests : IDisposable
         Assert.Equal(TaskStatus.Queued, (await _tasks.GetByIdAsync(t2.Id))!.Status);
     }
 
+    [Fact]
+    public async Task BatchUpdateTaskStatus_Done_MixedWorktreeState_ReportsPerItemAndDoesNotAbort()
+    {
+        var listId = await SeedListAsync();
+        var noWorktree = await SeedTaskAsync(listId, "no-wt", TaskStatus.Idle);
+        var missing = "does-not-exist";
+        var sut = BuildSut();
+
+        var results = await sut.BatchUpdateTaskStatus(
+            new[] { noWorktree.Id, missing }, "Done", CancellationToken.None);
+
+        Assert.True(results.Single(r => r.TaskId == noWorktree.Id).Ok);
+        Assert.False(results.Single(r => r.TaskId == missing).Ok);
+        Assert.Equal(TaskStatus.Done, (await _tasks.GetByIdAsync(noWorktree.Id))!.Status);
+    }
+
     [Fact]
     public async Task BatchTools_RejectEmptyBatch()
     {

tests/ClaudeDo.Worker.Tests/External/ExternalMcpServiceTests.cs

@@ -395,17 +395,47 @@ public sealed class ExternalMcpServiceTests : IDisposable
     }
 
     [Fact]
-    public async Task UpdateTaskStatus_Done_StillRejected()
+    public async Task UpdateTaskStatus_WaitingForReview_StillRejected()
     {
         var listId = await SeedListAsync();
         var task = await SeedTaskAsync(listId, status: TaskStatus.Idle);
         var sut = BuildSut(CreateQueue());
 
         var ex = await Assert.ThrowsAsync<InvalidOperationException>(
-            () => sut.UpdateTaskStatus(task.Id, "Done", CancellationToken.None));
+            () => sut.UpdateTaskStatus(task.Id, "WaitingForReview", CancellationToken.None));
         Assert.Contains("not settable externally", ex.Message);
     }
 
+    [Fact]
+    public async Task UpdateTaskStatus_Done_NoWorktree_SetsDoneAndFinishedAt()
+    {
+        var listId = await SeedListAsync();
+        var task = await SeedTaskAsync(listId, status: TaskStatus.Idle);
+        var sut = BuildSut(CreateQueue());
+
+        var dto = await sut.UpdateTaskStatus(task.Id, "Done", CancellationToken.None);
+
+        Assert.Equal("Done", dto.Status);
+        var loaded = await _tasks.GetByIdAsync(task.Id);
+        Assert.Equal(TaskStatus.Done, loaded!.Status);
+        Assert.NotNull(loaded.FinishedAt);
+    }
+
+    [Fact]
+    public async Task UpdateTaskStatus_Done_WithActiveWorktree_Throws()
+    {
+        if (!GitAvailable) return;
+        var (task, _, _) = await SeedWorktreeAsync(TaskStatus.WaitingForReview);
+        var sut = BuildSut(CreateQueue());
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => sut.UpdateTaskStatus(task.Id, "Done", CancellationToken.None));
+
+        Assert.Contains("active worktree", ex.Message, StringComparison.OrdinalIgnoreCase);
+        var loaded = await _tasks.GetByIdAsync(task.Id);
+        Assert.Equal(TaskStatus.WaitingForReview, loaded!.Status);
+    }
+
     private ExternalMcpService NewService() => BuildSut(CreateQueue());
 
     private async Task<string> SeedIdleTask(string title = "t")