feat: 导出设置支持展开/折叠（默认折叠）+ 恢复默认按钮

- 导出设置面板默认折叠，点击标题栏展开/收起，折叠栏显示当前分辨率摘要
- 折叠栏保留快速下载按钮，始终可用
- 新增🔄恢复默认按钮：一键重置分辨率/自定义/文件名/历史选择到初始状态（历史记录保留）

app.js

@@ -648,6 +648,28 @@ function onExportPresetChange() {
     refreshPreview();
 }
 
+// 导出设置面板展开/折叠（默认折叠）
+let exportSettingsOpen = false;
+function toggleExportSettings() {
+    exportSettingsOpen = !exportSettingsOpen;
+    const body = document.getElementById('exportSettingsBody');
+    const t = document.getElementById('exportToggle');
+    body.style.display = exportSettingsOpen ? 'block' : 'none';
+    t.textContent = exportSettingsOpen ? '▾' : '▸';
+}
+
+// 一键恢复默认（重置全部设置，历史记录保留）
+function resetExportSettings() {
+    document.getElementById('exportPreset').value = 'original';
+    document.getElementById('customResGroup').style.display = 'none';
+    document.getElementById('customWidth').value = '';
+    document.getElementById('customHeight').value = '';
+    document.getElementById('exportFilename').value = '';
+    document.getElementById('exportHistory').value = '';
+    refreshExportHint();
+    refreshPreview();
+}
+
 function onCustomResInput() {
     refreshExportHint();
     refreshPreview();
@@ -778,12 +800,13 @@ function exportCurrent(prefix) {
     }).catch(err => alert(err.message));
 }
 
-// 导出分辨率提示
+// 导出分辨率提示 + 折叠栏摘要
 function refreshExportHint() {
     const { w, h } = getResolution();
     const hint = document.getElementById('exportResHint');
-    if (!hint) return;
-    hint.textContent = w > 0 && h > 0 ? `导出分辨率：${w} × ${h}（原图居中缩放）` : '导出分辨率：原始大小';
+    if (hint) hint.textContent = w > 0 && h > 0 ? `导出分辨率：${w} × ${h}（原图居中缩放）` : '导出分辨率：原始大小';
+    const sum = document.getElementById('exportSummary');
+    if (sum) sum.textContent = w > 0 && h > 0 ? `${w} × ${h}` : '原始大小';
 }
 
 // 刷新导出预览：以原图为中心，居中展示保存后的图

index.html

@@ -208,47 +208,56 @@ C, 20, 30, 40</pre>
                     </div>
                 </div>
 
-                <!-- 导出设置 + 按钮 -->
+                <!-- 导出设置 + 按钮（默认折叠） -->
                 <div class="panel-section" id="exportSection">
-                    <h2>📤 导出设置</h2>
-
-                    <div class="config-group">
-                        <label>分辨率</label>
-                        <select id="exportPreset" onchange="onExportPresetChange()">
-                            <option value="original">原始大小</option>
-                            <option value="1920x1080">1920 × 1080</option>
-                            <option value="1280x720">1280 × 720</option>
-                            <option value="1024x768">1024 × 768</option>
-                            <option value="800x600">800 × 600</option>
-                            <option value="custom">自定义</option>
-                        </select>
-                    </div>
-
-                    <div class="config-group" id="customResGroup" style="display:none;">
-                        <label>自定义分辨率（宽 × 高）</label>
-                        <div class="res-input-row">
-                            <input type="number" id="customWidth" min="1" max="8192" placeholder="宽" oninput="onCustomResInput()">
-                            <span class="res-times">×</span>
-                            <input type="number" id="customHeight" min="1" max="8192" placeholder="高" oninput="onCustomResInput()">
+                    <div class="export-header">
+                        <div class="export-header-main" onclick="toggleExportSettings()" title="点击展开/折叠">
+                            <h2>📤 导出设置</h2>
+                            <span class="export-summary" id="exportSummary">原始大小</span>
+                            <span class="export-toggle" id="exportToggle">▸</span>
                         </div>
+                        <button class="btn btn-success btn-sm" onclick="exportImage('png')">📥 下载</button>
                     </div>
 
-                    <div class="config-group">
-                        <label>历史分辨率（最近5个）</label>
-                        <select id="exportHistory" onchange="onHistorySelect()">
-                            <option value="">— 暂无历史 —</option>
-                        </select>
-                    </div>
+                    <div id="exportSettingsBody" class="export-settings-body" style="display:none;">
+                        <div class="config-group">
+                            <label>分辨率</label>
+                            <select id="exportPreset" onchange="onExportPresetChange()">
+                                <option value="original">原始大小</option>
+                                <option value="1920x1080">1920 × 1080</option>
+                                <option value="1280x720">1280 × 720</option>
+                                <option value="1024x768">1024 × 768</option>
+                                <option value="800x600">800 × 600</option>
+                                <option value="custom">自定义</option>
+                            </select>
+                        </div>
 
-                    <div class="config-group">
-                        <label>文件名</label>
-                        <input type="text" id="exportFilename" placeholder="留空则按日期时间自动命名">
-                        <p class="hint-text" id="exportResHint"></p>
-                    </div>
+                        <div class="config-group" id="customResGroup" style="display:none;">
+                            <label>自定义分辨率（宽 × 高）</label>
+                            <div class="res-input-row">
+                                <input type="number" id="customWidth" min="1" max="8192" placeholder="宽" oninput="onCustomResInput()">
+                                <span class="res-times">×</span>
+                                <input type="number" id="customHeight" min="1" max="8192" placeholder="高" oninput="onCustomResInput()">
+                            </div>
+                        </div>
 
-                    <div class="btn-group">
-                        <button class="btn btn-success" onclick="exportImage('png')">📥 下载图片</button>
-                        <button class="btn btn-success" id="btnExportSvg" onclick="exportImage('svg')">📥 导出SVG</button>
+                        <div class="config-group">
+                            <label>历史分辨率（最近5个）</label>
+                            <select id="exportHistory" onchange="onHistorySelect()">
+                                <option value="">— 暂无历史 —</option>
+                            </select>
+                        </div>
+
+                        <div class="config-group">
+                            <label>文件名</label>
+                            <input type="text" id="exportFilename" placeholder="留空则按日期时间自动命名">
+                            <p class="hint-text" id="exportResHint"></p>
+                        </div>
+
+                        <div class="btn-group">
+                            <button class="btn btn-secondary" onclick="resetExportSettings()">🔄 恢复默认</button>
+                            <button class="btn btn-success" id="btnExportSvg" onclick="exportImage('svg')">📥 导出SVG</button>
+                        </div>
                     </div>
                 </div>
 

style.css

@@ -671,3 +671,54 @@ input[type="range"]::-moz-range-thumb {
     padding: 1px 8px;
     font-weight: 600;
 }
+
+/* ===== 导出设置折叠栏 ===== */
+.export-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    gap: 8px;
+}
+
+.export-header-main {
+    display: flex;
+    align-items: center;
+    gap: 10px;
+    flex: 1;
+    cursor: pointer;
+    user-select: none;
+    padding: 2px 0;
+}
+
+.export-header h2 {
+    font-size: 1rem;
+    margin: 0;
+    color: var(--text);
+}
+
+.export-summary {
+    font-size: 0.75rem;
+    color: var(--primary);
+    background: #eef2ff;
+    padding: 2px 8px;
+    border-radius: 10px;
+    font-weight: 600;
+    white-space: nowrap;
+}
+
+.export-toggle {
+    color: var(--text-light);
+    font-size: 0.8rem;
+    transition: transform 0.2s;
+}
+
+.export-settings-body {
+    margin-top: 12px;
+    padding-top: 12px;
+    border-top: 1px dashed var(--border);
+}
+
+.btn-sm {
+    padding: 6px 12px;
+    font-size: 0.82rem;
+}