feat(worker): chain a normal parent's children on WaitingForChildren

A standalone parent (PlanningPhase.None) with existing Idle/Queued children
now runs itself first, then sequences its children instead of flat-enqueuing
all of them at once: SubmitForChildrenAsync calls
PlanningChainCoordinator.SetupChainAsync(enqueue: true) right after the
Running -> WaitingForChildren transition, mirroring the planning path but
firing immediately instead of waiting for an explicit "Queue plan". Planning
parents are left untouched (they queue via QueuePlanAsync), and a child
already Running makes SetupChainAsync throw, which is now caught and logged
so it can't fail the parent's own transition.

src/ClaudeDo.Worker/CLAUDE.md

@@ -50,7 +50,7 @@ subfolder within their area; the namespace stays the area namespace.
 ## Architecture
 
 - **Program.cs** — loads config, inits schema, registers DI, configures SignalR on `/hub`, binds to `127.0.0.1:47821`
-- **TaskStateService** — the **only** component that writes `Status`, `PlanningPhase`, `BlockedByTaskId`, and the `task_dependencies` edges. All transitions return a `TransitionResult` (no exceptions on invalid moves). Wakes the queue and advances the planning chain on child terminal transitions. Every transition broadcasts via a private `NotifyAsync(taskId)` — never call `_broadcaster.TaskUpdated` directly from this class, `NotifyAsync` also drives `TicketStatusSync.SyncAsync` (see Tickets below) and a direct call skips that transition's ticket write-back. `SetDependsOnAsync` replaces the task's whole dependency **set** (empty list clears it) and rejects a self-reference, an unknown dependency id, or any link that would create a cycle — a BFS over the whole `task_dependencies` edge set from every proposed predecessor, so a multi-edge loop (A→B→C→A) is caught too, and one bad edge leaves the entire set unwritten.
+- **TaskStateService** — the **only** component that writes `Status`, `PlanningPhase`, `BlockedByTaskId`, and the `task_dependencies` edges. All transitions return a `TransitionResult` (no exceptions on invalid moves). Wakes the queue and advances the planning chain on child terminal transitions. `SubmitForChildrenAsync` (Running → WaitingForChildren) also chains and immediately queues a normal parent's own Idle/Queued children via `PlanningChainCoordinator.SetupChainAsync(enqueue: true)` — unlike a planning parent (`PlanningPhase != None`), whose children stay untouched here and wait for the user's explicit "Queue plan" (`QueuePlanAsync`); a child already `Running` makes `SetupChainAsync` throw, which is caught and logged rather than failing the parent's own transition. Every transition broadcasts via a private `NotifyAsync(taskId)` — never call `_broadcaster.TaskUpdated` directly from this class, `NotifyAsync` also drives `TicketStatusSync.SyncAsync` (see Tickets below) and a direct call skips that transition's ticket write-back. `SetDependsOnAsync` replaces the task's whole dependency **set** (empty list clears it) and rejects a self-reference, an unknown dependency id, or any link that would create a cycle — a BFS over the whole `task_dependencies` edge set from every proposed predecessor, so a multi-edge loop (A→B→C→A) is caught too, and one bad edge leaves the entire set unwritten.
 - **IQueueWaker / IQueuePicker / QueueService** — waker is a singleton `SemaphoreSlim`; picker performs the atomic `Queued → Running` claim filtered by `BlockedByTaskId IS NULL`, `is_manual = 0`, schedule, and "no `task_dependencies` edge whose predecessor isn't `done`" (doubly negated on purpose: zero edges stays eligible, all edges must be done, and an edge pointing at a vanished task keeps blocking); QueueService is a thin `BackgroundService` looping on the waker, dispatching via `TaskRunner`. Per tick it also applies the usage throttle and gate → [usage-monitoring](../../docs/explore-notes/usage-monitoring.md).
 - **RunCancellationRegistry** — taskId → running-run CTS. Lets `TaskStateService.CancelAsync` kill a cancelled task's process without a DI cycle.
 - **OverrideSlotService** — owns `RunNow` / `ContinueTask`; goes through `TaskStateService.StartRunningAsync` (caller-driven, serialized by slot lock).