Polish flowchart subtitle wording next time graph is touched

Backlog note only. Next time the Anvil Loop graph is touched, change the subtitle from `有问题就回炉，没问题才停止` to `必须处理才回炉，无阻塞则停止` so it aligns more tightly with the `必须处理？` decision node.

No blocker; do not prioritize separately.