fix(worker): close status-force bypasses on Running tasks

update_task_status Idle/Done, WorkerHub.SetTaskStatus, and the UI's Mark
Done/Cancelled menu items could all force a Running task's status without
going through TaskStateService's guards, leaving its CLI process untracked
and its worktree writes silently dropped. Idle now routes through the
already-guarded TaskStateService.ResetToIdleAsync instead of the repo's
unconditional ResetToManualAsync; Done and SetTaskStatus explicitly reject
Running; the context menu disables both entries with a tooltip while
running. TaskRunner also now logs a warning whenever a terminal transition
(SubmitForChildren/SubmitForReview/Complete/Fail) is rejected instead of
silently discarding the run result. DeleteTask's MCP path gets the same
friendly foreign-key message WorkerHub.DeleteTask already had for a task
with children.

src/ClaudeDo.Worker/Hub/WorkerHub.cs

@@ -586,6 +586,13 @@ public sealed class WorkerHub : Microsoft.AspNetCore.SignalR.Hub
     {
         if (!Enum.TryParse<TaskStatus>(status, ignoreCase: true, out var parsed))
             throw new HubException($"unknown status: {status}");
+
+        await using var ctx = await _dbFactory.CreateDbContextAsync(Context.ConnectionAborted);
+        var current = await new TaskRepository(ctx).GetByIdAsync(taskId, Context.ConnectionAborted)
+            ?? throw new HubException("task not found");
+        if (current.Status == TaskStatus.Running)
+            throw new HubException("Cannot change the status of a running task. Cancel it first.");
+
         // Queueing goes through the gated transition so draft subtasks can't be queued;
         // other statuses keep the unconditional "set status freely" affordance.
         var result = parsed == TaskStatus.Queued