fix(client): fix popout url (#8494)

packages/client/src/pages/theme-editor.vue

@@ -126,7 +126,7 @@ let changed = $ref(false);
 useLeaveGuard($$(changed));
 
 function showPreview() {
-	os.pageWindow('preview');
+	os.pageWindow('/preview');
 }
 
 function setBgColor(color: typeof bgColors[number]) {

packages/client/src/scripts/popout.ts

 import * as config from '@/config';
+import { appendQuery } from './url';
 
 export function popout(path: string, w?: HTMLElement) {
-	let url = path.startsWith('http://') || path.startsWith('https://') ? path : config.url + "/" + path;
-	url += '?zen';
+	let url = path.startsWith('http://') || path.startsWith('https://') ? path : config.url + path;
+	url = appendQuery(url, 'zen');
 	if (w) {
 		const position = w.getBoundingClientRect();
 		const width = parseInt(getComputedStyle(w, '').width, 10);