feat(mission-control): give the list handler its own review task

"Let Claude handle it" now creates one ClaudeDo task per run to host the
ConPTY session (Idle/IsManual, never queued) instead of an untracked
ad-hoc tile, so the run has a real title, diff, and review outcome.
Since the handler merges its own changes straight into the list's
working dir, the task never gets a WorktreeEntity; its review range
lives as new HandlerBaseCommit/HandlerHeadCommit columns on TaskEntity
instead, reusing the existing commit-range diff machinery and keeping
it out of the worktrees overview entirely.

tests/ClaudeDo.Worker.Tests/Runner/InteractiveLaunchSpecServiceTests.cs

@@ -70,6 +70,7 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
     private InteractiveLaunchSpecService BuildService() =>
         new(_db.CreateFactory(), _seeder, _registry,
             new WorktreeManager(new GitService(), _db.CreateFactory(), new WorkerConfig(), NullLogger<WorktreeManager>.Instance),
+            new GitService(),
             new WorkerConfig { ClaudeBin = _claudeStubPath });
 
     private async Task<string> SeedListAsync(string? workingDir = null, string name = "L")
@@ -477,6 +478,65 @@ public sealed class InteractiveLaunchSpecServiceTests : IDisposable
         Assert.Contains(t2, brief);
     }
 
+    // ── CreateMergeHelperTaskAsync ──
+
+    [Fact]
+    public async Task CreateMergeHelperTaskAsync_EmptyTaskIds_ThrowsInvalidOperation()
+    {
+        var listId = await SeedListAsync(workingDir: _tempDir);
+        var svc = BuildService();
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => svc.CreateMergeHelperTaskAsync(Array.Empty<string>(), listId, "title", "header", CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task CreateMergeHelperTaskAsync_UnknownList_ThrowsKeyNotFound()
+    {
+        var taskId = Guid.NewGuid().ToString();
+        var svc = BuildService();
+        await Assert.ThrowsAsync<KeyNotFoundException>(
+            () => svc.CreateMergeHelperTaskAsync(new[] { taskId }, "no-such-list", "title", "header", CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task CreateMergeHelperTaskAsync_ListWithoutExistingWorkingDir_ThrowsInvalidOperation()
+    {
+        var listId = await SeedListAsync(workingDir: Path.Combine(_tempDir, "gone"));
+        var taskId = Guid.NewGuid().ToString();
+        await SeedTaskAsync(taskId, listId, TaskStatus.WaitingForReview);
+
+        var svc = BuildService();
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => svc.CreateMergeHelperTaskAsync(new[] { taskId }, listId, "title", "header", CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task CreateMergeHelperTaskAsync_CreatesIdleManualTask_StampsHandlerBaseCommit()
+    {
+        if (!GitAvailable) { Assert.True(true, "git not available -- skipping"); return; }
+
+        var repo = CreateRepo();
+        var listId = await SeedListAsync(workingDir: repo.RepoDir, name: "Alpha");
+        var t1 = Guid.NewGuid().ToString();
+        await SeedTaskAsync(t1, listId, TaskStatus.WaitingForReview, title: "First task");
+
+        var svc = BuildService();
+        var newTaskId = await svc.CreateMergeHelperTaskAsync(
+            new[] { t1 }, listId, "List handler: Alpha", "Tasks handled by this run:", CancellationToken.None);
+
+        using var readCtx = _db.CreateContext();
+        var created = await new TaskRepository(readCtx).GetByIdAsync(newTaskId);
+        Assert.NotNull(created);
+        Assert.Equal("List handler: Alpha", created!.Title);
+        Assert.Equal(TaskStatus.Idle, created.Status);
+        Assert.True(created.IsManual);
+        Assert.Equal(repo.BaseCommit, created.HandlerBaseCommit);
+        Assert.Null(created.HandlerHeadCommit);
+        Assert.Contains("Tasks handled by this run:", created.Description);
+        Assert.Contains("First task", created.Description);
+        Assert.Contains(t1, created.Description);
+    }
+
     [Fact]
     public void BuildPlanningStart_MapsPlanningArgsAndEnv()
     {