Function onStreamingThinking

src/utils/messages.streamingThinking.test.ts:16–20

(
      update: (current: StreamingThinking | null) => StreamingThinking | null,
    )

    let currentThinking: StreamingThinking | null = null
    const onStreamingThinking = (
      update: (current: StreamingThinking | null) => StreamingThinking | null,
    ) => {
      currentThinking = update(currentThinking)
    }

    handleMessageFromStream(
      {