feat(online): live queue count — friends see each other waiting

The server only sent the queue size to the player who just joined, and the
client dropped the count entirely (emitMM ignored s.players). So two friends
queuing together never saw each other, even though the server does seat 2+
waiting humans together within ~25s.

- Server: BroadcastQueueLocked() pushes the current queue size to EVERY waiting
  player on join/cancel (not just the joiner).
- Client: thread the count through emitMM → MatchmakingState.waiting.
- MatchmakingScreen shows "N players in queue" (mm.inQueue) when ≥2 humans wait,
  so friends can tell they're queued together before bots fill the empty seats.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/Hokm.Server/Game/GameManager.cs

@@ -67,9 +67,10 @@ public sealed partial class GameManager
             if (_waiting.Any(w => w.player.UserId == p.UserId)) return;
             var timer = new Timer(_ => FlushTicket(p.UserId), null, QueueWaitMs, Timeout.Infinite);
             _waiting.Add((p, timer, DateTime.UtcNow));
-            _ = _hub.Clients.User(p.UserId).SendAsync("matchmaking",
-                new MatchmakingStateDto("searching", _waiting.Count, null));
             if (_waiting.Count >= 4) FormGroupLocked(4);
+            // Tell EVERYONE still waiting the new count (so friends queuing together
+            // see each other join), not just the player who just joined.
+            BroadcastQueueLocked();
         }
     }
 
@@ -78,10 +79,24 @@ public sealed partial class GameManager
         lock (_mmLock)
         {
             var idx = _waiting.FindIndex(w => w.player.UserId == userId);
-            if (idx >= 0) { _waiting[idx].timer.Dispose(); _waiting.RemoveAt(idx); }
+            if (idx >= 0)
+            {
+                _waiting[idx].timer.Dispose();
+                _waiting.RemoveAt(idx);
+                BroadcastQueueLocked();
+            }
         }
     }
 
+    /// <summary>Push the current queue size to every waiting player (call inside _mmLock).</summary>
+    private void BroadcastQueueLocked()
+    {
+        int n = _waiting.Count;
+        foreach (var w in _waiting)
+            _ = _hub.Clients.User(w.player.UserId).SendAsync("matchmaking",
+                new MatchmakingStateDto("searching", n, null));
+    }
+
     /// <summary>Client safety net: re-send the current game state to a player who
     /// may have missed the initial broadcast (green-felt freeze guard).</summary>
     public void Resync(string userId)