fix(game): own export chooser modal; PNG option outside in-app webviews only

Telegram's native showPopup delivers its callback with no user
activation, so navigator.share (TG iOS) and clipboard writes (TG
Android GCG copy) silently fail from it — the chooser is now always the
app's own modal, keeping the button click's gesture alive for the
delivery APIs.

The data:URL preview modal is dropped: the Android TG/VK long-press
menu mangles data: URLs (dead download, black-screen open, base64
clipboard garbage), so a binary PNG has no working client-side route in
those webviews at all. The image option is withheld there until the
server-rendered signed-URL delivery (Telegram downloadFile /
VKWebAppDownloadFile) lands; the plain web and mobile browsers keep it.

On-device findings by the owner on the test contour (TG iOS, TG
Android, VK Android).

ui/src/lib/share.test.ts

@@ -87,19 +87,13 @@ describe('pickImageDelivery', () => {
   const canShareNav = { canShare: () => true, share: async () => {} };
   const noShareNav = { canShare: () => false, share: async () => {} };
 
-  it('shares when the platform can share files, even in an in-app webview (iOS)', () => {
-    expect(pickImageDelivery(canShareNav, file, false)).toBe('share');
-    expect(pickImageDelivery(canShareNav, file, true)).toBe('share');
-  });
-
-  it('previews in an in-app webview that cannot share files (a binary PNG has no clipboard-text fallback)', () => {
-    expect(pickImageDelivery(noShareNav, file, true)).toBe('preview');
-    expect(pickImageDelivery(undefined, file, true)).toBe('preview');
+  it('shares when the platform can share files', () => {
+    expect(pickImageDelivery(canShareNav, file)).toBe('share');
   });
 
   it('downloads on a plain browser without Web Share (desktop)', () => {
-    expect(pickImageDelivery(noShareNav, file, false)).toBe('download');
-    expect(pickImageDelivery(undefined, file, false)).toBe('download');
+    expect(pickImageDelivery(noShareNav, file)).toBe('download');
+    expect(pickImageDelivery(undefined, file)).toBe('download');
   });
 });
 
@@ -121,7 +115,7 @@ describe('shareOrDownloadImage', () => {
     const share = vi.fn().mockRejectedValue(new DOMException('cancelled', 'AbortError'));
     const { createElement } = stubEnv(true, share);
 
-    expect(await shareOrDownloadImage(png(), false)).toBe('shared');
+    expect(await shareOrDownloadImage(png())).toBe('shared');
 
     expect(share).toHaveBeenCalledOnce();
     expect(createElement).not.toHaveBeenCalled();
@@ -130,20 +124,12 @@ describe('shareOrDownloadImage', () => {
   it('downloads via an anchor on a desktop browser that cannot share files', async () => {
     const { anchor, createElement } = stubEnv(false, vi.fn());
 
-    expect(await shareOrDownloadImage(png(), false)).toBe('downloaded');
+    expect(await shareOrDownloadImage(png())).toBe('downloaded');
 
     expect(createElement).toHaveBeenCalledWith('a');
     expect(anchor.click).toHaveBeenCalledOnce();
     expect(anchor.download).toBe('game-1.png');
   });
-
-  it('hands an in-app webview over to the preview modal (no share, no dead download)', async () => {
-    const { createElement } = stubEnv(false, vi.fn());
-
-    expect(await shareOrDownloadImage(png(), true)).toBe('preview');
-
-    expect(createElement).not.toHaveBeenCalled();
-  });
 });
 
 describe('pickTextShare', () => {