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

src/pages/ReportEditor.tsx

@@ -957,6 +957,7 @@ export default function ReportEditor() {
         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) {
           setDiffModal({
             isOpen: true,
@@ -982,7 +983,13 @@ export default function ReportEditor() {
     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.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(() => {