fix: sync language prefixes

src/layouts/PublicLayout.tsx

@@ -15,6 +15,7 @@ import {
   homePathForLang,
   isHomePathname,
   languageFromPathname,
+  localizePath,
   stripLangPrefix,
 } from "../languageRoutes";
 import { useLocalizedPath } from "../useLocalizedPath";
@@ -318,7 +319,15 @@ export function PublicLayout() {
   const homePath = homePathForLang(lang);
   const changeLang = (nextLang: Lang) => {
     setLang(nextLang);
-    if (isHome) nav(homePathForLang(nextLang), { replace: true });
+    if (isHome) {
+      nav(homePathForLang(nextLang), { replace: true });
+    } else {
+      // Preserve sub-path and query/hash; only swap the language prefix.
+      const canonical = stripLangPrefix(pathname);
+      nav(localizePath(canonical, nextLang) + search + hash, {
+        replace: true,
+      });
+    }
   };
   const footerInContentFlow = stripLangPrefix(pathname) === "/browse";
   // Current page name shown in the header brand slot (falls back to the brand).