add whisper download utils. add react-navigator.

app/index.tsx

@@ -1,10 +1,9 @@
-import { LanguageSelection } from "@/components/LanguageSelection";
-import { Link, Stack } from "expo-router";
+import { useNavigation } from '@react-navigation/native';
 import { useState } from "react";
 import { Image, Text, View, StyleSheet, Button, Pressable } from "react-native";
-import { Translator, language_matrix_entry } from "./i18n/api";
-import ConversationThread from "@/components/ConversationThread";
+import { LanguageServer, Translator, language_matrix_entry } from "./i18n/api";
 import { Conversation } from "./lib/conversation";
+import { LanguageSelection } from "@/components/LanguageSelection";
 
 function LogoTitle() {
   return (
@@ -16,21 +15,25 @@ function LogoTitle() {
 }
 
 export default function Home() {
+  const navigation = useNavigation();
+
   const [lang, setLang] = useState<language_matrix_entry | undefined>();
   const [conversation, setConversation] = useState<Conversation | undefined>();
   const [setShowSettings, showSettings] = useState<boolean>(false);
 
-  function onLangSelected(lang: language_matrix_entry | undefined) {
-    console.log("Language %s selected", lang?.code);
+  async function onLangSelected(lang: language_matrix_entry) {
+    console.log("Language %s selected", lang.code);
     setLang(lang);
     if (!lang?.code) return;
-    setConversation(
-      new Conversation(
-        new Translator("en", lang.code),
-        { id: "host", language: "en" },
-        { id: "guest", language: lang.code }
-      )
+    const langServer = await LanguageServer.getDefault();
+    const conversation = new Conversation(
+      new Translator("en", lang.code, langServer),
+      { id: "host", language: "en" },
+      { id: "guest", language: lang.code }
     );
+    navigation.navigate("Conversation", {
+      conversation,
+    });
   }
 
   function onGoBack() {
@@ -39,9 +42,7 @@ export default function Home() {
 
   return (
     <View style={styles.container}>
-      <Stack.Screen name="index" />
-      <Stack.Screen name="settings" />
-      <Stack.Screen name="conversation" />
+      <LanguageSelection onLangSelected={onLangSelected} />
     </View>
   );
 }