refactor(planning): dequeue orphans instead of promoting, restore lost lineage

Three behavioral changes around stuck planning subtasks:

- OrphanRecovery no longer clears ParentTaskId. Queued children of a
  parent that is not in a planning phase are dequeued (Status: Queued
  -> Idle, BlockedByTaskId cleared) but stay attached to the parent so
  the historical lineage is preserved.
- DiscardPlanningAsync stops promoting terminal (Done/Failed/Cancelled)
  children to top-level for the same reason - they remain ChildTasks of
  the (now non-planning) parent.
- New PlanningLineageRecovery hosted service scans
  ~/.todo-app/planning-sessions/ and re-attaches a single, unambiguous
  blocked-by chain to its original planning parent when the
  parent_task_id links were lost. Refuses to guess when multiple
  candidate chains exist.

UI now exposes ConnectionRestoredEvent on IWorkerClient, fired on first
connect and every reconnect. ListsIslandViewModel refreshes counters
and TasksIslandViewModel reloads the current list - so stale counts no
longer survive a worker restart.

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

tests/ClaudeDo.Ui.Tests/ViewModels/PlanningDiffViewModelTests.cs

@@ -13,6 +13,7 @@ public class PlanningDiffViewModelTests
         public event Action<string, string, DateTime>? TaskStartedEvent;
         public event Action<string, string, string, DateTime>? TaskFinishedEvent;
         public event Action<string>? TaskUpdatedEvent;
+        public event Action? ConnectionRestoredEvent;
         public event Action<string>? WorktreeUpdatedEvent;
         public event Action<string, string>? TaskMessageEvent;
         public event Action<string, string>? PlanningMergeStartedEvent;