refactor(qrcode): 优化布局逻辑，输入态隐藏预览区域

- 输入态：只显示输入框和生成按钮，隐藏二维码预览
- 预览态：上方显示文本预览（超长文本截断），下方显示二维码
- 点击编辑返回输入态，隐藏二维码预览
- 更新测试用例适配新布局

src/pages/QrCode/components/GeneratePanel.tsx

@@ -7,6 +7,9 @@ import { Button } from '@/components/ui/button';
 import { Label } from '@/components/ui/label';
 import { cn } from '@/lib/utils';
 
+/** 文本预览的最大显示字符数 */
+const TEXT_PREVIEW_MAX_LENGTH = 100;
+
 export default function GeneratePanel() {
   const { t } = useI18n('qrCode');
   const {
@@ -21,60 +24,40 @@ export default function GeneratePanel() {
   const isInputStep = generatorState.step === 'input';
   const hasText = generatorState.textToEncode.trim().length > 0;
 
-  return (
-    <div className="grid grid-cols-1 md:grid-cols-2 gap-6 w-full items-stretch select-none p-0.5">
-      {/* 左侧：输入态显示输入框，预览态显示文本预览 */}
-      <div
-        className={cn(
-          'border border-border rounded-xl bg-card text-card-foreground shadow-sm flex flex-col p-4',
-          isInputStep && 'focus-within:ring-1 focus-within:ring-ring focus-within:border-ring',
-        )}
-      >
-        <div className="flex flex-col space-y-2.5 h-full">
-          <div className="flex items-center justify-between">
+  /** 截断文本用于预览显示 */
+  const getTruncatedText = (text: string) => {
+    if (text.length <= TEXT_PREVIEW_MAX_LENGTH) return text;
+    return text.slice(0, TEXT_PREVIEW_MAX_LENGTH) + '...';
+  };
+
+  // 输入态：只显示输入框和生成按钮
+  if (isInputStep) {
+    return (
+      <div className="w-full select-none p-0.5">
+        <div
+          className={cn(
+            'border border-border rounded-xl bg-card text-card-foreground shadow-sm flex flex-col p-4',
+            'focus-within:ring-1 focus-within:ring-ring focus-within:border-ring',
+          )}
+        >
+          <div className="flex flex-col space-y-2.5">
             <Label className="text-[10px] font-bold text-muted-foreground/90 uppercase tracking-wider select-none pl-0.5">
-              {isInputStep ? t('qrCode:urlInputLabel') : t('qrCode:textPreviewLabel')}
+              {t('qrCode:urlInputLabel')}
             </Label>
 
-            {/* 预览态显示编辑按钮 */}
-            {!isInputStep && (
-              <Button variant="ghost" size="sm" onClick={backToEdit} className="h-7 px-2 text-xs">
-                <Pencil className="w-3 h-3 mr-1" />
-                {t('qrCode:editButton')}
-              </Button>
-            )}
-          </div>
+            <TextInputArea
+              value={generatorState.textToEncode}
+              onChange={setTextToEncode}
+              placeholder={t('qrCode:urlInputPlaceholder')}
+              showCount={true}
+              showClear={true}
+              allowCopy={false}
+              minRows={6}
+              maxRows={12}
+              externalError={generatorState.inputError || undefined}
+              onClear={() => setTextToEncode('')}
+            />
 
-          <div className="flex-1 min-h-0">
-            {isInputStep ? (
-              /* 输入态：可编辑的输入框 */
-              <TextInputArea
-                value={generatorState.textToEncode}
-                onChange={setTextToEncode}
-                placeholder={t('qrCode:urlInputPlaceholder')}
-                showCount={true}
-                showClear={true}
-                allowCopy={false}
-                minRows={6}
-                maxRows={12}
-                externalError={generatorState.inputError || undefined}
-                onClear={() => setTextToEncode('')}
-              />
-            ) : (
-              /* 预览态：只读文本预览 */
-              <div
-                className="h-full min-h-[150px] p-3 rounded-md border border-input bg-muted/50 overflow-auto"
-                title={generatorState.savedText}
-              >
-                <p className="text-sm text-foreground whitespace-pre-wrap break-all">
-                  {generatorState.savedText}
-                </p>
-              </div>
-            )}
-          </div>
-
-          {/* 输入态显示生成按钮 */}
-          {isInputStep && (
             <Button
               onClick={confirmGenerate}
               disabled={!hasText || generatorState.generating}
@@ -92,19 +75,40 @@ export default function GeneratePanel() {
                 </>
               )}
             </Button>
-          )}
+          </div>
+        </div>
+      </div>
+    );
+  }
+
+  // 预览态：显示文本预览 + 二维码
+  return (
+    <div className="w-full select-none p-0.5 space-y-4">
+      {/* 文本预览区域 */}
+      <div className="border border-border rounded-xl bg-card text-card-foreground shadow-sm p-4">
+        <div className="flex items-center justify-between mb-2">
+          <Label className="text-[10px] font-bold text-muted-foreground/90 uppercase tracking-wider select-none pl-0.5">
+            {t('qrCode:textPreviewLabel')}
+          </Label>
+          <Button variant="ghost" size="sm" onClick={backToEdit} className="h-7 px-2 text-xs">
+            <Pencil className="w-3 h-3 mr-1" />
+            {t('qrCode:editButton')}
+          </Button>
+        </div>
+        <div
+          className="text-sm text-foreground bg-muted/50 rounded-md p-3 cursor-default"
+          title={generatorState.savedText}
+        >
+          {getTruncatedText(generatorState.savedText)}
         </div>
       </div>
 
-      {/* 右侧：二维码预览区域 */}
-      <div className="flex flex-col h-full">
-        <QrCodePreview
-          qrCodeDataUrl={generatorState.qrCodeDataUrl}
-          onDownload={downloadQrCode}
-          onCopy={copyQrCode}
-          placeholderText={isInputStep ? t('qrCode:generateFirstHint') : undefined}
-        />
-      </div>
+      {/* 二维码预览区域 */}
+      <QrCodePreview
+        qrCodeDataUrl={generatorState.qrCodeDataUrl}
+        onDownload={downloadQrCode}
+        onCopy={copyQrCode}
+      />
     </div>
   );
 }