fix(export): VK Android viewer+clipboard; no share title on iOS

Round-5 on-device findings:

- VK Android's DownloadFile hangs regardless of Content-Length and
  Range/206 (PNG stalls ~80%, GCG at 0%) — the download route is
  abandoned there: the PNG opens in VK's native image viewer
  (VKWebAppShowImages — its save works on-device) and the GCG returns
  to the clipboard copy (the pre-URL route, always solid). VK iOS keeps
  VKWebAppDownloadFile (verified perfect); the desktop iframe keeps
  plain anchor downloads.
- The iOS share sheet no longer carries a title: iOS pasted the
  'game-<hash>.png' filename as accompanying text next to the image.

docs/ARCHITECTURE.md

@@ -798,9 +798,11 @@ service ever needs to know the public host) and hands it to the best affordance
 each platform has: Telegram Android/desktop `downloadFile` (Bot API 8.0; the
 chooser there is the native showPopup — activation-free bridge calls end to end),
 Telegram iOS the OS share sheet with the fetched file (the app-modal click supplies
-the user activation a popup callback lacks), VK mobile `VKWebAppDownloadFile` for
+the user activation a popup callback lacks), VK iOS `VKWebAppDownloadFile` for both
-both formats, the OS share sheet on a mobile browser, or a plain anchor download
+formats, VK Android the native image viewer (PNG) + the clipboard (GCG) — its
-(desktop browsers and the VK desktop iframe). The gateway serves the bytes via
+DownloadFile hangs regardless of Content-Length/Range — the OS share sheet on a
+mobile browser, or a plain anchor download (desktop browsers and the VK desktop
+iframe). The gateway serves the bytes via
 `http.ServeContent` (Content-Length + Range/206 — Android's system DownloadManager
 hangs on chunked bodies of unknown length). The GET is the gateway's
 **only unauthenticated data route** (`/dl/*` — in the caddy `@gateway` matcher and the

docs/FUNCTIONAL.md

@@ -345,9 +345,11 @@ stretches the board (never below its minimum) so the image carries no dead space
 Delivery is **one signed, short-lived link for both formats on every platform**,
 handed to the best affordance each platform has (each branch verified on-device):
 Telegram Android/desktop use Telegram's download dialog (whose own preview shares
-onwards); **Telegram iOS opens the OS share sheet** with the fetched file; on VK
+onwards); **Telegram iOS opens the OS share sheet** with the fetched file; VK iOS
-both formats go through VK's download into its native share/preview flow (the
+takes both formats through VK's download into its native share flow, while on the
-desktop VK iframe, an ordinary browser, downloads them); a **mobile browser gets
+**VK Android client** — whose downloader hangs — the image opens in VK's native
+photo viewer (saving from its controls) and the GCG copies to the clipboard (the
+desktop VK iframe, an ordinary browser, downloads both); a **mobile browser gets
 the OS share sheet** (nothing lands in Downloads first); a desktop browser
 downloads the file. The link needs no login to fetch (the platforms' downloaders
 carry none) and is valid for minutes. The single exception is a legacy Telegram

docs/FUNCTIONAL_ru.md

@@ -355,10 +355,12 @@ Telegram Android/desktop (там это безопасно: цепочка це
 платформе**, отданная лучшему механизму, который у платформы реально есть (каждая
 ветка проверена на устройстве): Telegram Android/desktop — диалог загрузки Telegram
 (из его превью файл шерится дальше); **Telegram iOS — системная share-шторка** со
-скачанным файлом; в VK оба формата идут через загрузку VK в её нативный
+скачанным файлом; VK iOS ведёт оба формата через загрузку VK в её нативный
-share/preview-поток (десктопный iframe VK — обычный браузер — скачивает файлы);
+share-поток, а на **VK Android** — чей загрузчик виснет — картинка открывается в
-**мобильный браузер получает системную share-шторку** (ничего не оседает в
+нативном просмотрщике фото VK (сохранение его кнопками), GCG копируется в буфер
-Загрузках); десктопный браузер скачивает файл. Ссылка не требует логина при
+(десктопный iframe VK — обычный браузер — скачивает оба); **мобильный браузер
+получает системную share-шторку** (ничего не оседает в Загрузках); десктопный
+браузер скачивает файл. Ссылка не требует логина при
 скачивании (родные загрузчики платформ его не несут) и живёт минуты. Единственное
 исключение — устаревший клиент Telegram без диалога загрузки (до Bot API 8.0): там
 GCG откатывается на прежнее копирование в буфер (с подтверждающим тостом), а пункт

docs/UI_DESIGN.md

@@ -414,10 +414,12 @@ enabled on the first, uncached load) and flip in place when an event refreshes t
   both options need the connection). Both formats mint the same signed relative link
   (`game.export_url`), resolved against the app's own origin, then delivered per platform
   (each branch owner-verified on-device): TG Android/desktop `downloadFile` (its preview
-  shares onwards); TG iOS the OS share sheet with the fetched file; VK mobile
+  shares onwards); TG iOS the OS share sheet with the fetched file; VK iOS
-  `VKWebAppDownloadFile` for both formats (VK's native share/preview flow), the VK desktop
+  `VKWebAppDownloadFile` for both formats (VK's native share flow); VK Android — whose
-  iframe plain anchor downloads; a mobile browser the OS share sheet (the proven
+  DownloadFile hangs — the PNG in VK's native image viewer (`VKWebAppShowImages`, its save
-  fetch-then-share pattern); a desktop browser an anchor download. A legacy Telegram
+  works) and the GCG to the clipboard; the VK desktop iframe plain anchor downloads; a
+  mobile browser the OS share sheet (the proven fetch-then-share pattern); a desktop
+  browser an anchor download. A legacy Telegram
   client without `downloadFile` keeps the old GCG clipboard copy, hides the image option
   and stays on the app modal. Confirming a resign reveals the full board: it closes the
   history drawer (portrait) and zooms the board out.

ui/src/game/Game.svelte

@@ -23,7 +23,7 @@
   import { alphabetLetters, hasAlphabet } from '../lib/alphabet';
   import { hintsLeft } from '../lib/hints';
   import { downloadUrl, shareOrDownloadGcg, shareUrlAsFile } from '../lib/share';
-  import { insideVK, vkCopyText, vkDownloadFile, vkPlatform } from '../lib/vk';
+  import { insideVK, vkAndroidWebView, vkCopyText, vkDownloadFile, vkPlatform, vkShowImages } 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';
@@ -939,8 +939,11 @@
   //   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
+  //   VK iOS               our modal (VK has no native chooser) → VKWebAppDownloadFile for
   //                        both formats — the client lands in its native share/preview flow.
+  //   VK Android           our modal → the PNG opens in VK's native image viewer (its save
+  //                        works; the Android DownloadFile hangs), the GCG copies to the
+  //                        clipboard (the pre-URL route, always solid there).
   //   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.
@@ -998,10 +1001,20 @@
       const mime = kind === 'png' ? 'image/png' : 'text/plain';
       if (insideTelegram() && !tgShareSheet && telegramDownloadFile(url, filename)) return;
       if (insideVK()) {
-        // Desktop iframe: an ordinary browser, both formats download by anchor. Mobile
+        // Per-VK-client delivery (each branch owner-verified): the iOS client's
-        // clients take VKWebAppDownloadFile into VK's native share/preview flow; a failed
+        // VKWebAppDownloadFile lands in a native share flow and is perfect; the ANDROID
-        // bridge call falls back to the anchor.
+        // client's download hangs indefinitely, so the PNG opens in VK's native image
-        if (!vkPlatform().startsWith('desktop') && (await vkDownloadFile(url, filename))) return;
+        // viewer (its "save" works) and the GCG goes to the clipboard; the desktop
+        // iframe is an ordinary browser — plain anchor downloads.
+        if (vkAndroidWebView()) {
+          if (kind === 'png' && (await vkShowImages(url))) return;
+          if (kind === 'gcg') {
+            void exportGcgLegacy();
+            return;
+          }
+        } else if (!vkPlatform().startsWith('desktop') && (await vkDownloadFile(url, filename))) {
+          return;
+        }
         downloadUrl(url, filename);
         return;
       }

ui/src/lib/share.ts

@@ -114,7 +114,9 @@ export async function shareUrlAsFile(url: string, filename: string, mime: string
       const file = new File([await resp.blob()], filename, { type: mime });
       if (nav.canShare({ files: [file] })) {
         try {
-          await nav.share({ files: [file], title: filename });
+          // No title: iOS pastes it as accompanying text next to the image; the named
+          // file speaks for itself.
+          await nav.share({ files: [file] });
         } catch {
           /* cancelled — intentionally a no-op */
         }

ui/src/lib/vk.ts

@@ -155,6 +155,21 @@ export async function vkShare(link: string): Promise<boolean> {
   }
 }
 
+/**
+ * vkShowImages opens VK's native image viewer on url — on the Android client this is the
+ * PNG delivery: the viewer's own "save" works there, while VKWebAppDownloadFile hangs
+ * indefinitely (on-device finding). Resolves false on any failure, 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