fix(e2e): Buffer body for the /dl route fulfill

route.fulfill silently never resolves a FETCH interception given a
Uint8Array body (a navigation download tolerates it), deadlocking the
new share-sheet test — the fetch promise hung, no share, no toast. A
node Buffer unblocks it. Also refreshes the spec header to the final
per-platform delivery matrix.

ui/e2e/export.spec.ts

@@ -1,11 +1,11 @@
+import { Buffer } from 'node:buffer';
 import { expect, test, type Page } from './fixtures';
 
-// The finished-game export: the history header's 📤 button opens the app's own format
-// chooser (never Telegram's native popup — its callback carries no user activation),
-// and BOTH formats travel the same unified route on every platform: the client mints a
-// signed relative URL (game.export_url), resolves it against its own origin and hands
-// it to the platform's native download — Telegram downloadFile / VKWebAppDownloadFile —
-// or a plain anchor download in a browser. g3 ("vs Rick") is the seeded finished game.
+// The finished-game export: one signed relative URL (game.export_url) resolved against
+// the app's own origin, delivered by the most native affordance per platform — Telegram's
+// showPopup chooser + downloadFile dialog (all bridge calls, activation-safe), VK's
+// native viewer/download, the OS share sheet with the fetched file on a mobile browser,
+// a plain anchor download on desktop. g3 ("vs Rick") is the seeded finished game.
 // The mock gateway returns a shape-faithful /dl/... path; the tests intercept that
 // route and serve bytes, so the download itself is exercised end to end.
 
@@ -13,9 +13,9 @@ import { expect, test, type Page } from './fixtures';
 const PNG_HEX =
   '89504e470d0a1a0a0000000d49484452000000010000000108060000001f15c489' +
   '0000000a49444154789c6360000000020001e221bc330000000049454e44ae426082';
-const PNG_BYTES = Uint8Array.from({ length: PNG_HEX.length / 2 }, (_, i) =>
-  parseInt(PNG_HEX.slice(i * 2, i * 2 + 2), 16),
-);
+// Buffer, not Uint8Array: route.fulfill silently hangs a FETCH interception on a
+// Uint8Array body (a navigation download tolerates it) — the share test deadlocked.
+const PNG_BYTES = Buffer.from(PNG_HEX, 'hex');
 
 async function routeDl(page: Page): Promise<void> {
   await page.route('**/dl/**', (route) => {