feat(planning): consolidate finalize+chain via TaskStateService, fix queue pickup

Slice 4 of the worker state consolidation refactor. Eliminates the
"queue never picks up planning tasks" bug structurally by routing both
the manager and MCP finalize paths through TaskStateService and
PlanningChainCoordinator.SetupChainAsync, where the auto-wake on enqueue
guarantees the queue picker claims the first child immediately.

- Delete TaskRepository.FinalizePlanningAsync; PlanningSessionManager
  now orchestrates via _state.FinalizePlanningAsync + _chain.SetupChainAsync.
- Rename QueueSubtasksSequentiallyAsync to SetupChainAsync (internal);
  layout is now Status=Queued + BlockedByTaskId, with auto-attached agent tag.
- OnChildFinishedAsync looks up the successor by BlockedByTaskId, drops
  the legacy Waiting status lookup.
- PlanningMcpService.Finalize routes through state+chain; EditableStatuses
  drops Waiting and adds Idle; gate uses PlanningPhase==Active.
- TaskStateService.FinalizePlanningAsync clears the planning session token.
- UI: TaskRowViewModel adds BlockedByTaskId; IsQueued/IsWaiting reflect
  the new layout; TasksIslandViewModel.RemoveFromQueueAsync clears
  BlockedByTaskId on dequeue.
- New regression test PlanningEndToEndTests.FinalizeAsync_FirstChildIs
  ClaimedByPicker_WithinDeadline asserts the picker claims the first
  child within 200ms with no manual WakeQueue.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Worker/Program.cs

@@ -83,6 +83,7 @@ builder.Services.AddSingleton(sp =>
         sp.GetRequiredService<GitService>(),
         cfg,
         sp.GetRequiredService<ITaskStateService>(),
+        sp.GetRequiredService<PlanningChainCoordinator>(),
         planningSessionsDir));
 builder.Services.AddSingleton<IPlanningTerminalLauncher>(sp =>
     new WindowsTerminalPlanningLauncher("wt.exe", cfg.ClaudeBin));