feat(ui): force Mini App fullscreen on mobile, not via the share link

Replace the shared-link &mode=fullscreen (which would also force fullscreen on
desktop) with an imperative requestFullscreen() on launch, gated to mobile
clients (ios/android/android_x) — mirroring how Telegram's own Mini Apps go
immersive on phones while desktop keeps the bot's full-size window. It triggers
the existing fullscreenChanged -> safe-area resync; a no-op on clients predating
Bot API 8.0.

ui/src/lib/telegram.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { insideTelegram, telegramClosingConfirmation, telegramLaunch } from './telegram';
+import { insideTelegram, telegramClosingConfirmation, telegramLaunch, telegramRequestFullscreen } from './telegram';
 
 function stubWebApp(initData: string, startParam?: string) {
   vi.stubGlobal('window', {
@@ -38,22 +38,28 @@ describe('telegram launch detection', () => {
   });
 });
 
+// stubClient stands up a fake WebApp on the given platform with spies for the mobile-gated
+// chrome toggles, so the platform gate can be asserted without a real Telegram client.
+function stubClient(platform?: string) {
+  const enable = vi.fn();
+  const disable = vi.fn();
+  const requestFullscreen = vi.fn();
+  vi.stubGlobal('window', {
+    Telegram: {
+      WebApp: { platform, enableClosingConfirmation: enable, disableClosingConfirmation: disable, requestFullscreen },
+    },
+  });
+  return { enable, disable, requestFullscreen };
+}
+
+const mobilePlatforms = ['ios', 'android', 'android_x'];
+const desktopPlatforms = ['tdesktop', 'macos', 'web', undefined];
+
 describe('telegramClosingConfirmation', () => {
   afterEach(() => vi.unstubAllGlobals());
 
-  // stubClient stands up a fake WebApp on the given platform with spies for the close-guard
-  // toggles, so the platform gate can be asserted without a real Telegram client.
-  function stubClient(platform?: string) {
-    const enable = vi.fn();
-    const disable = vi.fn();
-    vi.stubGlobal('window', {
-      Telegram: { WebApp: { platform, enableClosingConfirmation: enable, disableClosingConfirmation: disable } },
-    });
-    return { enable, disable };
-  }
-
   it('arms the close guard on mobile clients', () => {
-    for (const p of ['ios', 'android']) {
+    for (const p of mobilePlatforms) {
       const { enable } = stubClient(p);
       telegramClosingConfirmation(true);
       expect(enable, `platform=${p}`).toHaveBeenCalledOnce();
@@ -61,7 +67,7 @@ describe('telegramClosingConfirmation', () => {
   });
 
   it('skips the close guard on desktop clients (the dialog there is just noise)', () => {
-    for (const p of ['tdesktop', 'macos', 'web', undefined]) {
+    for (const p of desktopPlatforms) {
       const { enable } = stubClient(p);
       telegramClosingConfirmation(true);
       expect(enable, `platform=${p}`).not.toHaveBeenCalled();
@@ -74,3 +80,23 @@ describe('telegramClosingConfirmation', () => {
     expect(disable).toHaveBeenCalledOnce();
   });
 });
+
+describe('telegramRequestFullscreen', () => {
+  afterEach(() => vi.unstubAllGlobals());
+
+  it('goes immersive fullscreen on mobile clients', () => {
+    for (const p of mobilePlatforms) {
+      const { requestFullscreen } = stubClient(p);
+      telegramRequestFullscreen();
+      expect(requestFullscreen, `platform=${p}`).toHaveBeenCalledOnce();
+    }
+  });
+
+  it('leaves desktop clients as a standard window (the bot full-size setting fills it)', () => {
+    for (const p of desktopPlatforms) {
+      const { requestFullscreen } = stubClient(p);
+      telegramRequestFullscreen();
+      expect(requestFullscreen, `platform=${p}`).not.toHaveBeenCalled();
+    }
+  });
+});