fix(ui): also resync an open game on a foreground regain without a stream drop

Closes the residual tail of the previous commit: when the live stream stays
alive across a brief suspend (Telegram/iOS can pause the socket without tearing
it down), an in-game event shed from a full hub buffer is never recovered by
the reconnect refetch (no reconnect) or the open-game poll (it only runs while
the stream is down). Mirror the lobby's focus re-poll: bump app.resync on a
foreground regain that did not drop the stream, and have Game.svelte refetch
the open game once per resync. Also rescues a missed move/game_over after a
suspend. Add a silent-join mock seam + an e2e isolating this path; extend the
ARCHITECTURE §10 fallback note.

ui/src/game/Game.svelte

@@ -263,6 +263,17 @@
     return () => clearInterval(timer);
   });
 
+  // (C) Returning to the foreground without the stream having dropped (so (A) does not fire) may
+  // still have missed an event shed from a full hub buffer while suspended; refetch once per resync.
+  let lastResync = app.resync;
+  $effect(() => {
+    const r = app.resync;
+    if (r !== lastResync) {
+      lastResync = r;
+      void load();
+    }
+  });
+
   function isCoarse(): boolean {
     return typeof matchMedia !== 'undefined' && matchMedia('(pointer: coarse)').matches;
   }