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.