feat(planning): gate subtask queueing behind plan finalization

Planning subtasks are now "Draft" until their parent plan is finalized,
then "Planned" (queueable). Finalizing a plan no longer auto-queues the
child chain; the user sends the plan to the queue explicitly.

- TaskStateService rejects a child entering Queued/Running unless its parent
  is Finalized; this single invariant covers UI, queue, RunNow and MCP paths
- WorkerHub.SetTaskStatus routes Queued through the gated EnqueueAsync
- Finalize call sites pass queueAgentTasks: false
- PlanningChainCoordinator.QueuePlanAsync guards the chain build on Finalized
- TaskRowViewModel derives Draft/Planned from ParentFinalized; gates
  CanSendToQueue / CanQueuePlan; view shows a PLANNED badge

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/ClaudeDo.Worker.Tests/UiVm/TaskRowViewModelPlanningTests.cs

@@ -46,4 +46,55 @@ public class TaskRowViewModelPlanningTests
         Assert.False(vm.IsPlanningParent);
         Assert.Null(vm.PlanningBadge);
     }
+
+    [Fact]
+    public void DraftChild_CannotSendToQueue()
+    {
+        var vm = MakeRow(TaskStatus.Idle, parentTaskId: "parent-id");
+        vm.ParentFinalized = false;
+        Assert.True(vm.IsDraft);
+        Assert.False(vm.IsPlanned);
+        Assert.False(vm.CanSendToQueue);
+    }
+
+    [Fact]
+    public void PlannedChild_CanSendToQueue()
+    {
+        var vm = MakeRow(TaskStatus.Idle, parentTaskId: "parent-id");
+        vm.ParentFinalized = true;
+        Assert.False(vm.IsDraft);
+        Assert.True(vm.IsPlanned);
+        Assert.True(vm.CanSendToQueue);
+    }
+
+    [Fact]
+    public void StandaloneIdle_CanSendToQueue()
+    {
+        var vm = MakeRow(TaskStatus.Idle);
+        Assert.False(vm.IsChild);
+        Assert.True(vm.CanSendToQueue);
+    }
+
+    [Fact]
+    public void FinalizedParentWithChildren_CanQueuePlan()
+    {
+        var vm = MakeRow(TaskStatus.Idle, phase: PlanningPhase.Finalized);
+        vm.HasPlanningChildren = true;
+        Assert.True(vm.CanQueuePlan);
+    }
+
+    [Fact]
+    public void ActiveParentWithChildren_CannotQueuePlan()
+    {
+        var vm = MakeRow(TaskStatus.Idle, phase: PlanningPhase.Active);
+        vm.HasPlanningChildren = true;
+        Assert.False(vm.CanQueuePlan);
+    }
+
+    [Fact]
+    public void FinalizedParentWithoutChildren_CannotQueuePlan()
+    {
+        var vm = MakeRow(TaskStatus.Idle, phase: PlanningPhase.Finalized);
+        Assert.False(vm.CanQueuePlan);
+    }
 }