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/lib/app.svelte.ts

@@ -55,6 +55,10 @@ export const app = $state<{
   notifications: number;
   /** Unread chat-message count per game id, for the in-game score-bar and 💬 badges. */
   chatUnread: Record<string, number>;
+  /** Monotonic counter bumped when the app returns to the foreground without the live stream
+   *  having dropped. An open game watches it to refetch once, recovering an in-game event shed
+   *  from a full hub buffer while suspended (the stream-drop case is covered by streamAlive). */
+  resync: number;
 }>({
   ready: false,
   streamAlive: false,
@@ -70,6 +74,7 @@ export const app = $state<{
   localeLocked: false,
   notifications: 0,
   chatUnread: {},
+  resync: 0,
 });
 
 let unsubscribeStream: (() => void) | null = null;
@@ -104,7 +109,13 @@ function goForeground(): void {
   backgrounded = false;
   foregroundedAt = Date.now();
   if (!app.session) return;
-  if (!app.streamAlive) openStream(); // silently re-establish a stream dropped while away
+  if (!app.streamAlive) {
+    openStream(); // re-establish a stream dropped while away (its reconnect refetch then runs)
+  } else {
+    // The stream stayed alive across the suspend, so the reconnect refetch will not fire — but an
+    // event may have been shed from a full hub buffer while away; nudge an open game to refetch.
+    app.resync++;
+  }
   void refreshNotifications();
 }