feat(i18n): extract remaining screens into en/zh-Hans catalogs; full Simplified Chinese coverage (closes #68) (#103)

Extends the i18n infra from #97 (Settings screen only) to the rest of the
app: session chat screen, connection add/edit/list screens, sessions list
(incl. directory grouping from #96), navigation titles, notifications
category metadata, error boundary, telemetry consent modal, auth gate, and
every chat UI component (permission/question prompts, status indicator,
model/variant pickers, directory switcher/browser, reasoning block, tool
call card, session info).

- 244 new keys added to en.json/zh-Hans.json with reviewed, natural
  Simplified Chinese (not machine-garbage), keeping key sets identical.
- User content, server URLs, code snippets, log/error-detail text, and
  diagnostics-classify.ts (pure dependency-free module feeding Sentry/
  support reports) are intentionally left untranslated per scope.
- Interpolation used for counts/names (e.g. reconnect attempt, files
  count, connection name in delete confirmations); categoryMeta/
  CONNECTION_TYPES switched to labelKey indirection since they're
  module-level constants evaluated before i18next is guaranteed ready.
- Added src/lib/i18n/catalog-parity.test.ts (node --test) asserting
  en.json/zh-Hans.json expose identical key sets and no empty values,
  to catch future locale drift.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

app/_layout.tsx

@@ -5,7 +5,7 @@ import { useColorScheme, View, ActivityIndicator } from "react-native"
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query"
 import { GestureHandlerRootView } from "react-native-gesture-handler"
 import { BottomSheetModalProvider } from "@gorhom/bottom-sheet"
-import { I18nextProvider } from "react-i18next"
+import { I18nextProvider, useTranslation } from "react-i18next"
 import i18n from "../src/lib/i18n/config"
 import { useAuth } from "../src/stores/auth"
 import { useConnections } from "../src/stores/connections"
@@ -25,6 +25,7 @@ const queryClient = new QueryClient()
 function RootLayout() {
   const colorScheme = useColorScheme()
   const isDark = colorScheme === "dark"
+  const { t } = useTranslation()
 
   const { initialize: initAuth, isLoading: authLoading } = useAuth()
   const { loadConnections, isLoading: connectionsLoading, client } = useConnections()
@@ -129,21 +130,21 @@ function RootLayout() {
               <Stack.Screen
                 name="session/[id]"
                 options={{
-                  title: "Session",
+                  title: t("session.titleFallback"),
                   presentation: "card",
                 }}
               />
               <Stack.Screen
                 name="connection/add"
                 options={{
-                  title: "Add Connection",
+                  title: t("nav.addConnectionTitle"),
                   presentation: "modal",
                 }}
               />
               <Stack.Screen
                 name="connection/[id]"
                 options={{
-                  title: "Edit Connection",
+                  title: t("nav.editConnectionTitle"),
                   presentation: "modal",
                 }}
               />