Method setSourceViewMode

src/core/nodeviews/code-block.ts:753–861

* 设置源码模式

(enabled: boolean)

   * 设置源码模式
   */
  private setSourceViewMode(enabled: boolean): void {
    if (this.sourceViewMode === enabled) return;
    this.sourceViewMode = enabled;

    if (enabled) {
      // 进入源码模式
      this.dom.classList.add("source-view");

      // 隐藏头部
      if (this.headerElement) {
        this.headerElement.style.display = "none";
      }

      // 隐藏 Mermaid 预览
      if (this.mermaidPreview) {
        this.mermaidPreview.style.display = "none";
      }

      // 隐藏 CodeMirror
      if (this.editorContainer) {
        this.editorContainer.style.display = "none";
      }

      // 创建源码容器（拆分成多行以参与行号计数）
      if (!this.sourceTextElement) {
        this.sourceTextElement = document.createElement("div");
        this.sourceTextElement.className = "milkup-code-block-source-container";
        this.sourceTextElement.contentEditable = "true";
        this.sourceTextElement.spellcheck = false;
        this.sourceTextElement.style.cssText = `
          position: relative;
          font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
          font-size: 14px;
          line-height: 1.6;
          padding: 0;
          margin: 0;
          color: inherit;
          background: transparent;
          border: none;
          outline: none;
        `;

        // 监听输入事件
        this.sourceTextElement.addEventListener("input", () => {
          this.handleSourceTextInput();
        });

        // 监听键盘事件
        this.sourceTextElement.addEventListener("keydown", (e) => {
          this.handleSourceTextKeydown(e);
        });

        // 阻止默认的粘贴行为，使用纯文本粘贴
        this.sourceTextElement.addEventListener("paste", (e) => {
          e.preventDefault();
          const text = e.clipboardData?.getData("text/plain") || "";
          document.execCommand("insertText", false, text);
        });