fix(editor): AI注入后Ctrl+Z失效 + 字体格式统一

- confirmAiInjection改用Range.selectNodeContents + execCommand('insertHTML')保留浏览器撤销栈
- handleAIGenerate中对cleanHtml增加<p>标签内联样式注入：padding 0px、font-family SimSun、font-size 12pt、line-height 1.5
- 确保AI替换后的文字字体与原有文字完全一致

工程分析/20260419_2030/实现方案.md

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+# 实现方案
+
+## 修改文件
+- `src/pages/ReportEditor.tsx`
+
+## 修改 1：`confirmAiInjection` 保留撤销栈（约 line 981-998）
+
+**原代码**：
+```tsx
+  const confirmAiInjection = (newHtml: string, regionId: string) => {
+    if (!editorRef.current) return;
+    const targetContent = editorRef.current.querySelector(`.ai-region[data-ai-id="${regionId}"] .ai-content`) as HTMLElement;
+    if (targetContent) {
+      targetContent.innerHTML = newHtml;
+      targetContent.style.transition = 'background-color 0.3s ease';
+      targetContent.style.backgroundColor = '#bfdbfe';
+      setTimeout(() => {
+        targetContent.style.backgroundColor = '#eff6ff';
+        setTimeout(() => {
+          targetContent.style.backgroundColor = 'transparent';
+        }, 800);
+      }, 400);
+      contentRef.current = editorRef.current.innerHTML;
+      saveDraftToStorage();
+    }
+    setDiffModal(null);
+  };
+```
+
+**新代码**：
+```tsx
+  const confirmAiInjection = (newHtml: string, regionId: string) => {
+    if (!editorRef.current) return;
+    const targetContent = editorRef.current.querySelector(`.ai-region[data-ai-id="${regionId}"] .ai-content`) as HTMLElement;
+    if (targetContent) {
+      targetContent.focus();
+      const sel = window.getSelection();
+      const range = document.createRange();
+      range.selectNodeContents(targetContent);
+      sel?.removeAllRanges();
+      sel?.addRange(range);
+      document.execCommand('insertHTML', false, newHtml);
+      targetContent.style.transition = 'background-color 0.3s ease';
+      targetContent.style.backgroundColor = '#bfdbfe';
+      setTimeout(() => {
+        targetContent.style.backgroundColor = '#eff6ff';
+        setTimeout(() => {
+          targetContent.style.backgroundColor = 'transparent';
+        }, 800);
+      }, 400);
+      contentRef.current = editorRef.current.innerHTML;
+      saveDraftToStorage();
+    }
+    setDiffModal(null);
+  };
+```
+
+**变更点**：
+1. 去掉 `targetContent.innerHTML = newHtml;`
+2. 增加 `targetContent.focus()`
+3. 使用 `Range.selectNodeContents(targetContent)` 选中区域内所有旧内容
+4. 使用 `document.execCommand('insertHTML', false, newHtml)` 执行替换
+5. 浏览器撤销栈会记录这次替换，Ctrl+Z 可正常撤销
+
+## 修改 2：`handleAIGenerate` 中 `<p>` 标签注入样式（约 line 955-970）
+
+**原代码**：
+```tsx
+      if (responseJson.updatedHtml && aiModifyEnabled) {
+        let cleanHtml = responseJson.updatedHtml;
+        cleanHtml = cleanHtml.replace(/<br\s*\/?>/gi, '');
+        cleanHtml = cleanHtml.replace(/<\/p>\s*<p>/gi, '</p><p>');
+        cleanHtml = cleanHtml.trim();
+        if (targetRegionEl) {
+```
+
+**新代码**：
+```tsx
+      if (responseJson.updatedHtml && aiModifyEnabled) {
+        let cleanHtml = responseJson.updatedHtml;
+        cleanHtml = cleanHtml.replace(/<br\s*\/?>/gi, '');
+        cleanHtml = cleanHtml.replace(/<\/p>\s*<p>/gi, '</p><p>');
+        cleanHtml = cleanHtml.trim();
+        cleanHtml = cleanHtml.replace(/<p>/gi, '<p style="padding: 0px; font-family: SimSun; font-size: 12pt; line-height: 1.5;">');
+        if (targetRegionEl) {
+```
+
+**变更点**：在 `cleanHtml.trim()` 后增加一行正则替换，将所有 `<p>` 标签替换为带标准内联样式的 `<p>` 标签。
+
+**样式值说明**：
+- `padding: 0px`：与原始段落一致
+- `font-family: SimSun`：宋体
+- `font-size: 12pt`：12pt 字号
+- `line-height: 1.5`：1.5 倍行高