feat(claude-do): feat(queue): Option pro Liste — Tasks mit überlappendem Date

## Befund (Batch-Lauf 2026-08-06, Liste "Bandel.Hub")
maxParallelExecutions = 5, 23 Geschwister-Tasks auf demselben Plugin. Die Parallelitaet hat die
Ausfuehrung verkuerzt, aber die Konfliktlast erhoeht: eine CSS-Datei wurde von 10 Tasks
angefasst, drei Razor-Dateien von je 6. Der Engpass des Gesamtdurchlaufs war nicht die
Ausfuehrung, sondern Review und Merge — die sind zwingend seriell. Netto wa

ClaudeDo-Task: 89f989e0-4fcf-43f5-a802-11d63df7a6d1

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

@@ -172,4 +172,48 @@ public sealed class QueueStateMcpToolsTests : IDisposable
 
         Assert.Equal(new[] { first.Id, second.Id }, result.WaitingTaskIds);
     }
+
+    [Fact]
+    public async Task GetQueueState_ScopeBlockedTasks_Empty_WhenNoListSerializes()
+    {
+        var listId = await SeedListAsync();
+        var (_, sut) = CreateSut();
+
+        var running = await SeedTaskAsync(listId, TaskStatus.Running);
+        running.ScopeGlobs = "src/Foo.cs";
+        await _ctx.SaveChangesAsync();
+        var queued = await SeedTaskAsync(listId, TaskStatus.Queued);
+        queued.ScopeGlobs = "src/Foo.cs";
+        await _ctx.SaveChangesAsync();
+
+        var result = await sut.GetQueueState(CancellationToken.None);
+
+        Assert.Contains(queued.Id, result.WaitingTaskIds);
+        Assert.Empty(result.ScopeBlockedTasks);
+    }
+
+    [Fact]
+    public async Task GetQueueState_ScopeBlockedTasks_ReportsReasonAndBlocker_WhenListSerializes()
+    {
+        var listId = await SeedListAsync();
+        await _listRepo.SetConfigAsync(new ListConfigEntity { ListId = listId, SerializeOnFileOverlap = true });
+
+        var (_, sut) = CreateSut();
+
+        var running = await SeedTaskAsync(listId, TaskStatus.Running);
+        running.ScopeGlobs = "src/Foo.cs";
+        await _ctx.SaveChangesAsync();
+
+        var queued = await SeedTaskAsync(listId, TaskStatus.Queued);
+        queued.ScopeGlobs = "src/Foo.cs";
+        await _ctx.SaveChangesAsync();
+
+        var result = await sut.GetQueueState(CancellationToken.None);
+
+        Assert.Contains(queued.Id, result.WaitingTaskIds);
+        var reason = Assert.Single(result.ScopeBlockedTasks);
+        Assert.Equal(queued.Id, reason.TaskId);
+        Assert.Equal(running.Id, reason.BlockedByTaskId);
+        Assert.Equal("scope_overlap", reason.Reason);
+    }
 }