Release 4.2.6+1: fix sidebar RU/EN and theme toggles — applyTheme param shadowed i18n t(), so init threw and click listeners never bound. Windows 4.2.6.1.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/appui/index.html

@@ -2440,8 +2440,10 @@
       } catch (_) {}
       return "light";
     }
-    function applyTheme(t) {
-      const theme = t === "dark" ? "dark" : "light";
+    // Param must not be named `t` — that shadows the i18n helper and throws on title update,
+    // aborting script init so theme/lang click listeners never bind (4.2.5 regression).
+    function applyTheme(next) {
+      const theme = next === "dark" ? "dark" : "light";
       document.documentElement.setAttribute("data-theme", theme);
       try { localStorage.setItem(THEME_KEY, theme); } catch (_) {}
       if (themeToggle) {
@@ -2451,24 +2453,34 @@
       if (themeSwitch) themeSwitch.checked = theme === "dark";
     }
     applyTheme(document.documentElement.getAttribute("data-theme") || readTheme());
-    if (themeToggle) {
-      themeToggle.addEventListener("click", () => {
-        const cur = document.documentElement.getAttribute("data-theme") === "dark" ? "dark" : "light";
-        applyTheme(cur === "dark" ? "light" : "dark");
+    // Event delegation on stable parents (survives future re-renders; not disabled by busy).
+    const sideFoot = document.querySelector(".side-foot");
+    if (sideFoot) {
+      sideFoot.addEventListener("click", (e) => {
+        const langBtn = e.target.closest("button[data-lang]");
+        if (langBtn && sideFoot.contains(langBtn)) {
+          setLang(langBtn.getAttribute("data-lang"));
+          return;
+        }
+        const themeBtn = e.target.closest("#themeToggle, .theme-toggle");
+        if (themeBtn && sideFoot.contains(themeBtn)) {
+          const cur = document.documentElement.getAttribute("data-theme") === "dark" ? "dark" : "light";
+          applyTheme(cur === "dark" ? "light" : "dark");
+        }
       });
     }
     if (themeSwitch) {
       themeSwitch.addEventListener("change", () => applyTheme(themeSwitch.checked ? "dark" : "light"));
     }
-
-    function wireLangSeg(root) {
-      if (!root) return;
-      root.querySelectorAll("button[data-lang]").forEach((b) => {
-        b.addEventListener("click", () => setLang(b.getAttribute("data-lang")));
+    const langSegSettings = $("langSegSettings");
+    if (langSegSettings) {
+      langSegSettings.addEventListener("click", (e) => {
+        const langBtn = e.target.closest("button[data-lang]");
+        if (langBtn && langSegSettings.contains(langBtn)) {
+          setLang(langBtn.getAttribute("data-lang"));
+        }
       });
     }
-    wireLangSeg($("langSeg"));
-    wireLangSeg($("langSegSettings"));
     applyTranslations();
 
     function skippedVersion() {