fix(ui): route external links out of the Android VK WebView

The Android VK client's WebView ignores target=_blank and navigates the
Mini App's own window to the target, stranding the player outside the
game with no way back (the dictionary lookup, About/Feedback links, the
ad banner and the bot-link modal fallbacks). vk-bridge 3.x has no method
to open an external URL, so external links are routed through VK's own
leave-VK redirect (vk.com/away.php), which the client intercepts
natively and hands to the system browser.

onExternalLinkClick moves from lib/telegram to a new lib/links that
composes the Telegram and VK routers; iOS and desktop VK open _blank
correctly and are left alone.

ui/src/lib/vk.test.ts

@@ -1,5 +1,15 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { insideVK, onVKPath, vkAppId, vkLaunchParams, vkStartParam, appearanceForBg } from './vk';
+import {
+  insideVK,
+  onVKPath,
+  routeExternalLinkInVK,
+  vkAndroidWebView,
+  vkAppId,
+  vkExternalBrowserUrl,
+  vkLaunchParams,
+  vkStartParam,
+  appearanceForBg,
+} from './vk';
 
 describe('vk launch detection', () => {
   afterEach(() => vi.unstubAllGlobals());
@@ -50,6 +60,65 @@ describe('vk launch params', () => {
   });
 });
 
+describe('vk external links', () => {
+  afterEach(() => vi.unstubAllGlobals());
+
+  function stubVK(platform: string) {
+    const open = vi.fn();
+    vi.stubGlobal('location', {
+      pathname: '/vk/',
+      search: `?vk_user_id=1&vk_platform=${platform}&sign=x`,
+      href: 'https://app.example/vk/',
+      origin: 'https://app.example',
+    });
+    vi.stubGlobal('window', { open });
+    return open;
+  }
+
+  it('wraps a URL in the away.php redirect with the target encoded', () => {
+    const url = 'https://gramota.ru/poisk?query=кот&mode=slovari';
+    expect(vkExternalBrowserUrl(url)).toBe(`https://vk.com/away.php?to=${encodeURIComponent(url)}`);
+  });
+
+  it('detects the Android VK WebView from vk_platform', () => {
+    stubVK('mobile_android');
+    expect(vkAndroidWebView()).toBe(true);
+    stubVK('mobile_android_messenger');
+    expect(vkAndroidWebView()).toBe(true);
+    stubVK('mobile_iphone');
+    expect(vkAndroidWebView()).toBe(false);
+    stubVK('desktop_web');
+    expect(vkAndroidWebView()).toBe(false);
+  });
+
+  it('is not the Android WebView without a signed VK launch', () => {
+    vi.stubGlobal('location', { pathname: '/vk/', search: '?vk_platform=mobile_android' });
+    expect(vkAndroidWebView()).toBe(false);
+  });
+
+  it('routes an external _blank link through the away redirect on Android', () => {
+    const open = stubVK('mobile_android');
+    expect(routeExternalLinkInVK({ href: 'https://gramota.ru/poisk?query=кот', target: '_blank' })).toBe(true);
+    expect(open).toHaveBeenCalledWith(
+      `https://vk.com/away.php?to=${encodeURIComponent('https://gramota.ru/poisk?query=кот')}`,
+      '_blank',
+    );
+  });
+
+  it('leaves same-origin and non-_blank links to the browser', () => {
+    const open = stubVK('mobile_android');
+    expect(routeExternalLinkInVK({ href: 'https://app.example/lobby', target: '_blank' })).toBe(false);
+    expect(routeExternalLinkInVK({ href: 'https://gramota.ru', target: '' })).toBe(false);
+    expect(open).not.toHaveBeenCalled();
+  });
+
+  it('does nothing outside the Android VK client (iOS / desktop open _blank fine)', () => {
+    const open = stubVK('mobile_iphone');
+    expect(routeExternalLinkInVK({ href: 'https://gramota.ru', target: '_blank' })).toBe(false);
+    expect(open).not.toHaveBeenCalled();
+  });
+});
+
 describe('appearanceForBg', () => {
   it('maps a dark background to the dark appearance (light status-bar icons)', () => {
     expect(appearanceForBg('#0f1115')).toBe('dark');