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.

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
-        // 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;
+        // Per-VK-client delivery (each branch owner-verified): the iOS client's
+        // VKWebAppDownloadFile lands in a native share flow and is perfect; the ANDROID
+        // client's download hangs indefinitely, so the PNG opens in VK's native image
+        // 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