Method updateHeader

src/core/nodeviews/code-block.ts:1435–1441

* 更新头部

(language: string)

   * 更新头部
   */
  private updateHeader(language: string): void {
    if (this.headerElement) {
      const newHeader = this.createHeader(language);
      this.dom.replaceChild(newHeader, this.headerElement);
      this.headerElement = newHeader;
    }
  }

  /**
   * 设置 Mermaid 显示模式