🎨 style(titlebar): 调整 Windows 窗口按钮间距

- 为 Windows 自绘标题栏控制组增加 4px 间距
- 保持其他平台及按钮尺寸、圆角和交互不变
- 新增平台选择器与间距接线回归测试

frontend/src/App.css

@@ -411,6 +411,10 @@ body[data-theme='light'] .redis-viewer-workbench .ant-radio-button-wrapper-check
 }
 
 /* Custom Title Bar Close Button Hover */
+body[data-platform='windows'] .titlebar-window-controls {
+    gap: 4px;
+}
+
 .titlebar-close-btn:hover {
     background-color: #ff4d4f !important;
     color: #fff !important;

frontend/src/App.tsx

@@ -7111,6 +7111,7 @@ function App() {
                   <div style={{ minWidth: Math.max(40, Math.round(48 * effectiveUiScale)) }} />
               ) : (
                   <div
+                    className="titlebar-window-controls"
                     data-no-titlebar-toggle="true"
                     onDoubleClick={(e) => e.stopPropagation()}
                     style={{ display: 'flex', height: '100%', WebkitAppRegion: 'no-drag', '--wails-draggable': 'no-drag' } as any}

frontend/src/App.window-controls-spacing.test.ts

@@ -0,0 +1,15 @@
+import { readFileSync } from 'node:fs';
+import { describe, expect, it } from 'vitest';
+
+const appSource = readFileSync(new URL('./App.tsx', import.meta.url), 'utf8');
+const appCssSource = readFileSync(new URL('./App.css', import.meta.url), 'utf8');
+
+describe('Windows titlebar window controls spacing', () => {
+  it('adds a small platform-scoped gap between the custom window buttons', () => {
+    expect(appSource).toContain('className="titlebar-window-controls"');
+    expect(appSource).toContain("document.body.setAttribute('data-platform', runtimePlatform || '')");
+    expect(appCssSource).toMatch(
+      /body\[data-platform='windows'\]\s+\.titlebar-window-controls\s*\{[^}]*gap:\s*4px;/s,
+    );
+  });
+});