fix(export): per-platform polish from the on-device review

- TG iOS: the OS share sheet with the fetched file (WKWebView has
  navigator.share — the долгоживущий debug-overlay Share path proves
  it). The chooser stays the app modal on this one platform: a native
  popup callback cannot supply the user activation the sheet needs.
  TG Android/desktop keep the native popup + downloadFile (verified
  perfect, untouched).
- VK mobile: the PNG now rides VKWebAppDownloadFile like the GCG — the
  owner-verified path that lands in VK's native share flow; the
  ShowImages viewer is dropped (its preview offered save only, no
  share).
- VK desktop iframe: both formats are plain anchor downloads (it is an
  ordinary browser; the viewer/bridge path made no sense there).

ui/e2e/export.spec.ts

@@ -70,6 +70,7 @@ test('inside Telegram the chooser is the native popup and delivery the native do
         WebApp: {
           initData: 'query_id=test&user=%7B%22id%22%3A1%7D&auth_date=1&hash=deadbeef',
           initDataUnsafe: {},
+          platform: 'android',
           ready() {},
           expand() {},
           showPopup(params: { buttons?: { id?: string; type?: string }[] }, cb: (id: string) => void) {
@@ -142,6 +143,60 @@ test('a mobile browser gets the OS share sheet with the fetched file', async ({
   expect(shared.type).toBe('image/png');
 });
 
+test('Telegram on iOS keeps the app chooser and opens the OS share sheet', async ({ page }) => {
+  // TG iOS: WKWebView has navigator.share, and the sheet is the preferred delivery — but
+  // it needs the user activation a native-popup callback cannot provide, so the chooser
+  // stays the app modal on this one platform.
+  await page.addInitScript(() => {
+    const shared: { name: string; type: string }[] = [];
+    Object.defineProperty(navigator, 'canShare', { value: () => true, configurable: true });
+    Object.defineProperty(navigator, 'share', {
+      value: async (data: { files?: File[] }) => {
+        for (const f of data.files ?? []) shared.push({ name: f.name, type: f.type });
+      },
+      configurable: true,
+    });
+    (window as unknown as { __shared: typeof shared }).__shared = shared;
+    Object.assign(window, {
+      Telegram: {
+        WebApp: {
+          initData: 'query_id=test&user=%7B%22id%22%3A1%7D&auth_date=1&hash=deadbeef',
+          initDataUnsafe: {},
+          platform: 'ios',
+          ready() {},
+          expand() {},
+          showPopup() {
+            (window as unknown as { __popupCalled?: boolean }).__popupCalled = true;
+          },
+          downloadFile() {
+            (window as unknown as { __downloadCalled?: boolean }).__downloadCalled = true;
+          },
+        },
+      },
+    });
+  });
+  await routeDl(page);
+  await page.goto('/');
+  await expect(page.getByText('Your turn')).toBeVisible();
+  await page.getByRole('button', { name: /Rick/ }).click();
+  await expect(page.locator('[data-cell]').first()).toBeVisible();
+  await page.locator('.scoreboard').click();
+  await page.getByRole('button', { name: 'Export game' }).click();
+
+  // The app modal opened (both formats) — the native popup was not used…
+  await expect(page.getByRole('button', { name: 'Image (PNG)' })).toBeVisible();
+  await page.getByRole('button', { name: 'Image (PNG)' }).click();
+  // …and the artifact went to the OS share sheet, not TG's download dialog.
+  await expect
+    .poll(() => page.evaluate(() => (window as unknown as { __shared: unknown[] }).__shared))
+    .toHaveLength(1);
+  const flags = await page.evaluate(() => {
+    const w = window as unknown as { __popupCalled?: boolean; __downloadCalled?: boolean };
+    return { popup: !!w.__popupCalled, download: !!w.__downloadCalled };
+  });
+  expect(flags).toEqual({ popup: false, download: false });
+});
+
 test('a legacy Telegram client (no downloadFile) hides the image and copies the GCG', async ({ page }) => {
   await page.addInitScript(() => {
     // Headless engines deny the real clipboard; a permissive stub keeps the legacy

ui/src/game/Game.svelte

@@ -23,11 +23,11 @@
   import { alphabetLetters, hasAlphabet } from '../lib/alphabet';
   import { hintsLeft } from '../lib/hints';
   import { downloadUrl, shareOrDownloadGcg, shareUrlAsFile } from '../lib/share';
-  import { insideVK, vkCopyText, vkDownloadFile, vkShowImages } from '../lib/vk';
+  import { insideVK, vkCopyText, vkDownloadFile, vkPlatform } from '../lib/vk';
   import { getCachedGame, setCachedGame, setCachedDraft, type CachedGame } from '../lib/gamecache';
   import { patchLobbyGame } from '../lib/lobbycache';
   import { applyGameOver, applyMoveDelta, applyOpponentJoined, type DeltaResult } from '../lib/gamedelta';
-  import { insideTelegram, telegramCanDownloadFile, telegramDialogsAvailable, telegramDownloadFile, telegramShowConfirm, telegramShowPopup } from '../lib/telegram';
+  import { insideTelegram, telegramCanDownloadFile, telegramDialogsAvailable, telegramDownloadFile, telegramPlatform, telegramShowConfirm, telegramShowPopup } from '../lib/telegram';
   import { haptic } from '../lib/haptics';
   import {
     BLANK,
@@ -933,25 +933,26 @@
 
   // The finished-game export offers two formats — the GCG file and the server-rendered PNG
   // image — behind one 📤 button, both minted as one signed relative URL and delivered by
-  // the most platform-native affordance:
-  //   Telegram   native showPopup chooser → native downloadFile dialog. All-native and
-  //              activation-safe: a popup callback carries no user activation, but the
-  //              whole TG chain is bridge calls, never gesture-gated Web APIs.
-  //   VK         our modal chooser (VK has no native one) → the PNG opens in VK's native
-  //              image viewer (VKWebAppShowImages — on screen at once, save/share from the
-  //              viewer's own controls); the GCG goes through VKWebAppDownloadFile; either
-  //              falls back to a plain anchor download when the bridge call fails (the
-  //              desktop iframe is an ordinary browser).
-  //   browsers   our modal → the OS share sheet with the fetched file where files can be
-  //              shared (mobile), else a plain anchor download (desktop).
+  // the best affordance each platform actually has (every branch owner-verified on-device):
+  //   TG Android/desktop   native showPopup chooser → native downloadFile dialog (whose own
+  //                        preview shares onwards). All bridge calls — activation-safe.
+  //   TG iOS               our modal chooser → the OS share sheet (WKWebView has
+  //                        navigator.share; a native-popup callback could not open it — no
+  //                        user activation — so the chooser stays the app modal here).
+  //   VK mobile            our modal (VK has no native chooser) → VKWebAppDownloadFile for
+  //                        both formats — the client lands in its native share/preview flow.
+  //   VK desktop iframe    our modal → plain anchor downloads (an ordinary browser).
+  //   mobile browsers      our modal → the OS share sheet with the fetched file.
+  //   desktop browsers     our modal → plain anchor download.
   let exportOpen = $state(false);
-  // The only platform without the URL delivery is a legacy Telegram client predating
-  // Bot API 8.0 downloadFile: the GCG falls back to the old clipboard copy there, and
-  // the image option is not offered (and the chooser stays our modal).
-  const exportImageAvailable = $derived(!insideTelegram() || telegramCanDownloadFile());
+  // TG iOS shares via the OS sheet regardless of Bot API 8.0; elsewhere in Telegram a
+  // legacy client without downloadFile keeps the old GCG clipboard copy and hides the
+  // image option (and the chooser stays our modal).
+  const tgShareSheet = $derived(insideTelegram() && telegramPlatform() === 'ios');
+  const exportImageAvailable = $derived(!insideTelegram() || tgShareSheet || telegramCanDownloadFile());
 
   async function onExportClick() {
-    if (insideTelegram() && telegramCanDownloadFile() && telegramDialogsAvailable()) {
+    if (insideTelegram() && !tgShareSheet && telegramCanDownloadFile() && telegramDialogsAvailable()) {
       const choice = await telegramShowPopup({
         message: t('game.exportChoice'),
         buttons: [
@@ -984,7 +985,7 @@
   // the URL so the server-rendered image matches what the player would have seen locally.
   const EXPORT_ACTIONS = ['pass', 'exchange', 'resign', 'timeout'] as const;
   async function exportArtifact(kind: 'png' | 'gcg') {
-    if (insideTelegram() && !telegramCanDownloadFile()) {
+    if (insideTelegram() && !tgShareSheet && !telegramCanDownloadFile()) {
       void exportGcgLegacy();
       return;
     }
@@ -994,14 +995,19 @@
       const timeZone = Intl.DateTimeFormat().resolvedOptions().timeZone ?? '';
       const { path, filename } = await gateway.exportUrl(id, kind, dateLocale, labels, timeZone);
       const url = new URL(path, location.origin).href;
-      if (insideTelegram() && telegramDownloadFile(url, filename)) return;
+      const mime = kind === 'png' ? 'image/png' : 'text/plain';
+      if (insideTelegram() && !tgShareSheet && telegramDownloadFile(url, filename)) return;
       if (insideVK()) {
-        if (kind === 'png' && (await vkShowImages(url))) return;
-        if (kind === 'gcg' && (await vkDownloadFile(url, filename))) return;
+        // Desktop iframe: an ordinary browser, both formats download by anchor. Mobile
+        // clients take VKWebAppDownloadFile into VK's native share/preview flow; a failed
+        // bridge call falls back to the anchor.
+        if (!vkPlatform().startsWith('desktop') && (await vkDownloadFile(url, filename))) return;
         downloadUrl(url, filename);
         return;
       }
-      const outcome = await shareUrlAsFile(url, filename, kind === 'png' ? 'image/png' : 'text/plain');
+      // TG iOS and plain browsers: the OS share sheet with the fetched file (falls back to
+      // a download where files cannot be shared — the desktop browser).
+      const outcome = await shareUrlAsFile(url, filename, mime);
       if (outcome === 'failed') showToast(t('error.generic'), 'error');
     } catch (e) {
       handleError(e);

ui/src/lib/telegram.ts

@@ -387,6 +387,12 @@ export function telegramCanDownloadFile(): boolean {
   return !!webApp()?.downloadFile;
 }
 
+/** telegramPlatform returns the SDK's platform tag ('ios', 'android', 'tdesktop', …) or ''
+ *  outside Telegram — the export delivery branches on it (iOS gets the OS share sheet). */
+export function telegramPlatform(): string {
+  return webApp()?.platform ?? '';
+}
+
 /**
  * telegramDownloadFile asks Telegram to download url as fileName through its native
  * dialog — the Mini App file delivery that works on every Telegram platform (a webview

ui/src/lib/vk.ts

@@ -155,20 +155,6 @@ export async function vkShare(link: string): Promise<boolean> {
   }
 }
 
-/**
- * vkShowImages opens VK's native image viewer on url — the image is on screen at once and
- * the viewer's own controls save/share it, which beats a blind background download for a
- * picture. Resolves false on any failure or outside VK, so the caller can fall back.
- */
-export async function vkShowImages(url: string): Promise<boolean> {
-  try {
-    await (await bridge()).send('VKWebAppShowImages', { images: [url] });
-    return true;
-  } catch {
-    return false;
-  }
-}
-
 /**
  * vkDownloadFile downloads url as filename through the VK client (VKWebAppDownloadFile) —
  * the mobile in-app file delivery, where the webview ignores <a download>. Resolves false