fix(ui): copy GCG to clipboard on Android in-app WebViews

On-device diagnostics from Android Telegram and VK confirmed both expose
no navigator.share AND no navigator.canShare, so the export fell to a Blob
<a download> that those WebViews silently ignore — nothing happened.

pickGcgDelivery is now a 3-way decision: Web Share where available (iOS),
a clipboard copy in an Android in-app WebView (Telegram/VK: no share, dead
download), else a desktop Blob download. shareOrDownloadGcg reports the
outcome so the game shows a "GCG copied" toast; the copy is VKWebAppCopyText
inside VK (which also covers the desktop VK iframe, where navigator.clipboard
is blocked) and navigator.clipboard otherwise.

Unit tests cover the 3-way choice and the copy/failed outcomes; new i18n key
game.gcgCopied (en+ru); docs ARCHITECTURE/FUNCTIONAL(+ru)/UI_DESIGN/TESTING.

docs/FUNCTIONAL.md

@@ -312,7 +312,8 @@ Finished games are archived in a dictionary-independent form and exportable to
 GCG; the export is offered **only once a game is finished**, and never for an
 honest-AI practice game (a live game's export would leak the move journal; an AI
 game is throwaway). The client shares the `.gcg` file where the platform supports
-it, otherwise downloads it. Statistics (durable accounts only):
+it; on an Android in-app client (Telegram / VK), which has neither Web Share nor a working file
+download, it copies the GCG to the clipboard (with a confirming toast); otherwise it downloads the file. Statistics (durable accounts only):
 wins, losses, draws, max points in a game, and max points for a single move (the
 best play, which already includes every word it formed plus the all-tiles bonus). It
 also shows the player's **move count** (their plays — passes and exchanges do not