feat(worker): queue interactive messages by default, interrupt opt-in

StreamingClaudeSession now buffers a mid-turn user message in a FIFO queue and
flushes one when the turn's result arrives (no implicit interrupt). InterruptAsync
only writes the control_request (no-op when idle); the resulting turn-end then
flushes any queued message. New InteractiveSessionService.InterruptAsync +
WorkerHub.InterruptInteractiveSession + IWorkerClient.InterruptInteractiveSessionAsync.

src/ClaudeDo.Ui/Services/WorkerClient.cs

@@ -303,6 +303,12 @@ public partial class WorkerClient : ObservableObject, IAsyncDisposable, IWorkerC
         catch { /* offline */ }
     }
 
+    public async Task InterruptInteractiveSessionAsync(string taskId)
+    {
+        try { await _hub.InvokeAsync("InterruptInteractiveSession", taskId); }
+        catch { /* offline */ }
+    }
+
     public Task<PendingQuestionDto?> GetPendingQuestionAsync(string taskId)
         => TryInvokeAsync<PendingQuestionDto>("GetPendingQuestion", taskId);