refactor: replace hardcoded NATS subjects with typed helpers

Add GameSubject/ChatSubject helpers to connect4 and snake packages,
eliminating magic string concatenation from handlers and main.go.

features/snakegame/handlers.go

@@ -114,7 +114,7 @@ func HandleSnakeEvents(snakeStore *snake.SnakeStore, nc *nats.Conn, sm *scs.Sess
 
 		// Subscribe to game updates via NATS
 		gameCh := make(chan *nats.Msg, 64)
-		gameSub, err := nc.ChanSubscribe("snake."+gameID, gameCh)
+		gameSub, err := nc.ChanSubscribe(snake.GameSubject(gameID), gameCh)
 		if err != nil {
 			return
 		}
@@ -126,7 +126,7 @@ func HandleSnakeEvents(snakeStore *snake.SnakeStore, nc *nats.Conn, sm *scs.Sess
 		var room *chat.Room
 
 		if sg.Mode == snake.ModeMultiplayer {
-			room = chat.NewRoom(nc, "snake.chat."+gameID)
+			room = chat.NewRoom(nc, snake.ChatSubject(gameID))
 			chatCh, chatSub, err = room.Subscribe()
 			if err != nil {
 				return
@@ -247,7 +247,7 @@ func HandleSendChat(snakeStore *snake.SnakeStore, nc *nats.Conn, sm *scs.Session
 			Message:  signals.ChatMsg,
 		}
 
-		room := chat.NewRoom(nc, "snake.chat."+gameID)
+		room := chat.NewRoom(nc, snake.ChatSubject(gameID))
 		room.Send(msg)
 
 		sse := datastar.NewSSE(w, r)