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/State/TaskStateServiceTests.cs

@@ -100,6 +100,30 @@ public sealed class TaskStateServiceTests : IDisposable
         Assert.Equal(TaskStatus.Running, await GetStatusAsync(id));
     }
 
+    [Fact]
+    public async Task EnqueueAsync_DraftChild_Rejected_WhenParentNotFinalized()
+    {
+        var parent = await SeedTaskAsync(TaskStatus.Idle, phase: PlanningPhase.Active);
+        var child = await SeedTaskAsync(TaskStatus.Idle, parentId: parent);
+
+        var result = await _sut.EnqueueAsync(child, default);
+
+        Assert.False(result.Ok);
+        Assert.Equal(TaskStatus.Idle, await GetStatusAsync(child));
+    }
+
+    [Fact]
+    public async Task EnqueueAsync_PlannedChild_Succeeds_WhenParentFinalized()
+    {
+        var parent = await SeedTaskAsync(TaskStatus.Idle, phase: PlanningPhase.Finalized);
+        var child = await SeedTaskAsync(TaskStatus.Idle, parentId: parent);
+
+        var result = await _sut.EnqueueAsync(child, default);
+
+        Assert.True(result.Ok);
+        Assert.Equal(TaskStatus.Queued, await GetStatusAsync(child));
+    }
+
     // ─── StartRunningAsync ────────────────────────────────────────────────
 
     [Fact]
@@ -142,6 +166,30 @@ public sealed class TaskStateServiceTests : IDisposable
         Assert.Equal(TaskStatus.Running, await GetStatusAsync(id));
     }
 
+    [Fact]
+    public async Task StartRunningAsync_DraftChild_Rejected_WhenParentNotFinalized()
+    {
+        var parent = await SeedTaskAsync(TaskStatus.Idle, phase: PlanningPhase.Active);
+        var child = await SeedTaskAsync(TaskStatus.Idle, parentId: parent);
+
+        var result = await _sut.StartRunningAsync(child, DateTime.UtcNow, default);
+
+        Assert.False(result.Ok);
+        Assert.Equal(TaskStatus.Idle, await GetStatusAsync(child));
+    }
+
+    [Fact]
+    public async Task StartRunningAsync_PlannedChild_Succeeds_WhenParentFinalized()
+    {
+        var parent = await SeedTaskAsync(TaskStatus.Idle, phase: PlanningPhase.Finalized);
+        var child = await SeedTaskAsync(TaskStatus.Idle, parentId: parent);
+
+        var result = await _sut.StartRunningAsync(child, DateTime.UtcNow, default);
+
+        Assert.True(result.Ok);
+        Assert.Equal(TaskStatus.Running, await GetStatusAsync(child));
+    }
+
     // ─── CompleteAsync ────────────────────────────────────────────────────
 
     [Fact]