Method showContextMenu

src/core/nodeviews/code-block.ts:1165–1285

* 显示右键菜单

(e: MouseEvent)

   * 显示右键菜单
   */
  private async showContextMenu(e: MouseEvent): Promise<void> {
    // 移除已存在的右键菜单
    this.hideContextMenu();

    const isHeaderContextMenu = !!(e.target instanceof HTMLElement
      ? e.target.closest(".milkup-code-block-header")
      : null);

    const menu = document.createElement("div");
    menu.className = "milkup-context-menu";

    // 检查是否有选区
    const { main } = this.cm.state.selection;
    const hasSelection = !main.empty;

    // 检查剪贴板是否有内容（文本或图片）
    let hasClipboardContent = true; // 默认启用粘贴
    try {
      const items = await navigator.clipboard.read();
      hasClipboardContent = items.length > 0;
    } catch {
      // 如果 read() 不支持，尝试 readText()
      try {
        const text = await navigator.clipboard.readText();
        hasClipboardContent = text.length > 0;
      } catch {
        hasClipboardContent = true; // 默认启用粘贴
      }
    }

    // 复制
    const copyItem = this.createContextMenuItem("复制", !hasSelection, () => {
      const selectedText = this.cm.state.sliceDoc(main.from, main.to);
      navigator.clipboard.writeText(selectedText);
      this.hideContextMenu();
    });
    menu.appendChild(copyItem);

    // 剪切
    const cutItem = this.createContextMenuItem("剪切", !hasSelection, () => {
      const selectedText = this.cm.state.sliceDoc(main.from, main.to);
      navigator.clipboard.writeText(selectedText);
      this.cm.dispatch({
        changes: { from: main.from, to: main.to, insert: "" },
      });
      this.hideContextMenu();
    });
    menu.appendChild(cutItem);

    // 粘贴 - 使用 Clipboard API 读取文本
    const pasteItem = this.createContextMenuItem("粘贴", !hasClipboardContent, async () => {
      this.hideContextMenu();
      this.cm.focus();
      try {
        const text = await navigator.clipboard.readText();
        if (text) {
          const { main } = this.cm.state.selection;
          this.cm.dispatch({