Enhance ConnectionPlaceholder component to handle missing device IP with localized messages; update DeviceContext to manage IP state; improve CSS for touch actions in various components; update locale files for English and Chinese with new connection prompts.

client/src/components/ConnectionPlaceholder.tsx

@@ -1,31 +1,61 @@
+import { useMemo } from "react";
 import { useDevice } from "@/contexts/DeviceContext";
 import { Loader2, Wifi } from "lucide-react";
 import BottomNav from "@/components/BottomNav";
+import localeZh from "@/locales/data-zh.json";
+import localeZhHK from "@/locales/data-zh-HK.json";
+import localeEn from "@/locales/data-en.json";
+
+type ConnectLocale = (typeof localeZh)["connect"];
+
+function pickConnectLocale(): ConnectLocale {
+  const params = new URLSearchParams(window.location.search);
+  const lang = params.get("lang");
+  if (lang === "0") return localeEn.connect;
+  if (lang === "1") return localeZhHK.connect;
+  if (lang === "2") return localeZh.connect;
+  const nav = navigator.language.toLowerCase();
+  if (nav.startsWith("zh-hk") || nav.startsWith("zh-tw")) return localeZhHK.connect;
+  if (nav.startsWith("zh")) return localeZh.connect;
+  return localeEn.connect;
+}
+
+function fmt(template: string, vars: Record<string, string>): string {
+  let s = template;
+  for (const [k, v] of Object.entries(vars)) {
+    s = s.split(`{${k}}`).join(v);
+  }
+  return s;
+}
 
 /** 自动连接设备时的占位（替代原 ConnectScreen） */
 export default function ConnectionPlaceholder() {
-  const { ip, isConnecting, error } = useDevice();
+  const { ip, isConnecting, error, ipMissing } = useDevice();
+  const text = useMemo(pickConnectLocale, []);
 
   return (
     <div className="min-h-screen bg-black flex flex-col items-center justify-center px-6 pb-24">
       <div className="mb-6 flex size-[4.5rem] items-center justify-center rounded-[16px] border border-white/15">
         <Wifi size={28} className="text-[#00FFF6]/80" />
       </div>
-      {isConnecting ? (
+      {ipMissing ? (
+        <>
+          <p className="text-[15px] text-white/80 mb-2">{text.ipMissingTitle}</p>
+          <p className="text-[13px] text-white/45 text-center max-w-xs">{text.ipMissingDesc}</p>
+          <p className="text-[13px] text-[#00FFF6]/80 mt-3 font-mono">?ip=10.0.0.119</p>
+        </>
+      ) : isConnecting ? (
         <>
           <Loader2 size={28} className="animate-spin text-[#00FFF6] mb-3" />
-          <p className="text-[15px] text-white/70">Connecting to {ip}…</p>
+          <p className="text-[15px] text-white/70">{fmt(text.connecting, { ip })}</p>
         </>
       ) : (
         <>
-          <p className="text-[15px] text-white/80 mb-2">Connection failed</p>
+          <p className="text-[15px] text-white/80 mb-2">{text.failedTitle}</p>
           <p className="text-[13px] text-white/45 text-center max-w-xs">
-            {error ?? "Check the device IP and your network connection."}
-          </p>
-          <p className="text-[12px] text-white/30 mt-3">
-            Specify the device in the URL, e.g.{" "}
-            <span className="text-white/50">?ip=10.0.0.119</span>
+            {error ?? text.failedDesc}
           </p>
+          <p className="text-[12px] text-white/30 mt-3 text-center max-w-xs">{text.failedHint}</p>
         </>
       )}
       <BottomNav />

client/src/components/DesktopAIShell.tsx

@@ -92,7 +92,7 @@ export default function DesktopAIShell({ children }: { children: ReactNode }) {
           "min-w-0",
           showSplit
             ? "h-full min-h-0 overflow-y-auto overflow-x-hidden"
-            : "min-h-dvh overflow-x-hidden",
+            : "min-h-dvh max-h-dvh overflow-x-hidden overflow-y-auto overscroll-y-contain [touch-action:pan-y]",
         )}
         style={
           showSplit