chore(ui): TEMP lobby diagnostic for the Android fullscreen issue

Renders Telegram viewport/fullscreen state (isFullscreen, isExpanded, viewport
heights, innerH vs screenH, safe-area insets) in the lobby, inside Telegram
only, to diagnose why the app still opens fullscreen on Android with
requestFullscreen now iOS-only and no persisted state (fresh TG + test account).
REVERT before merge.

ui/src/lib/telegram.ts

@@ -14,6 +14,10 @@ interface TelegramWebApp {
   themeParams?: TelegramThemeParams;
   colorScheme?: 'light' | 'dark';
   isFullscreen?: boolean;
+  isExpanded?: boolean;
+  viewportHeight?: number;
+  viewportStableHeight?: number;
+  exitFullscreen?: () => void;
   safeAreaInset?: { top: number; bottom: number; left: number; right: number };
   contentSafeAreaInset?: { top: number; bottom: number; left: number; right: number };
   ready?: () => void;
@@ -469,6 +473,25 @@ export function collectTelegramDiag(): TelegramDiag {
   };
 }
 
+/**
+ * telegramChromeDiag is a TEMPORARY on-device readout of Telegram's viewport / fullscreen state,
+ * rendered in the lobby to debug the Android fullscreen-persistence issue (the app still opens
+ * fullscreen on Android even though requestFullscreen is now iOS-only). REMOVE before merge.
+ */
+export function telegramChromeDiag(): string {
+  const w = webApp();
+  if (!w) return 'no telegram';
+  const ih = typeof window === 'undefined' ? 0 : window.innerHeight;
+  const sh = typeof screen === 'undefined' ? 0 : screen.height;
+  return [
+    `platform: ${w.platform ?? '—'}  version: ${w.version ?? '—'}`,
+    `isFullscreen: ${w.isFullscreen}  isExpanded: ${w.isExpanded}`,
+    `viewportH: ${w.viewportHeight ?? '—'}  stableH: ${w.viewportStableHeight ?? '—'}`,
+    `innerH: ${ih}  screenH: ${sh}`,
+    `contentSafeTop: ${w.contentSafeAreaInset?.top ?? '—'}  safeTop: ${w.safeAreaInset?.top ?? '—'}`,
+  ].join('\n');
+}
+
 // --- Login Widget (web sign-in for account linking) ---
 
 // The Login Widget is the web (non-Mini-App) Telegram sign-in. It is used only to