feat: add in-game chat to Connect 4

Add real-time chat alongside the game board, mirroring the snake chat
implementation. Fix mobile layout for both C4 and snake chats — expand
chat to full width and reduce history height on small screens.

main.go

@@ -353,6 +353,9 @@ func main() {
 		nickname := c.Signal(sessionNickname)
 		colSignal := c.Signal(0)
 		showGuestPrompt := c.Signal(false)
+		chatMsg := c.Signal("")
+		var chatMessages []ui.C4ChatMessage
+		var chatMu sync.Mutex
 
 		goToLogin := c.Action(func() {
 			c.Session().Set("return_url", "/game/"+gameID)
@@ -434,8 +437,53 @@ func main() {
 			}
 		})
 
+		sendChat := c.Action(func() {
+			msg := chatMsg.String()
+			if msg == "" || gi == nil {
+				return
+			}
+			color := gi.GetPlayerColor(playerID)
+			if color == 0 {
+				return
+			}
+			g := gi.GetGame()
+			nick := ""
+			for _, p := range g.Players {
+				if p != nil && p.ID == playerID {
+					nick = p.Nickname
+					break
+				}
+			}
+			cm := ui.C4ChatMessage{
+				Nickname: nick,
+				Color:    color,
+				Message:  msg,
+				Time:     time.Now().UnixMilli(),
+			}
+			data, err := json.Marshal(cm)
+			if err != nil {
+				return
+			}
+			c.Publish("game.chat."+gameID, data)
+			chatMsg.SetValue("")
+		})
+
 		if gameExists {
 			c.Subscribe("game."+gameID, func(data []byte) { c.Sync() })
+
+			c.Subscribe("game.chat."+gameID, func(data []byte) {
+				var cm ui.C4ChatMessage
+				if err := json.Unmarshal(data, &cm); err != nil {
+					return
+				}
+				chatMu.Lock()
+				chatMessages = append(chatMessages, cm)
+				if len(chatMessages) > 50 {
+					chatMessages = chatMessages[len(chatMessages)-50:]
+				}
+				chatMu.Unlock()
+				c.Sync()
+			})
 		}
 
 		if gameExists && sessionNickname != "" && gi.GetPlayerColor(playerID) == 0 {
@@ -480,13 +528,19 @@ func main() {
 				return dropPiece.OnClick(via.WithSignalInt(colSignal, col))
 			}
 
+			chatMu.Lock()
+			msgs := make([]ui.C4ChatMessage, len(chatMessages))
+			copy(msgs, chatMessages)
+			chatMu.Unlock()
+			chat := ui.C4Chat(msgs, chatMsg.Bind(), sendChat.OnClick(), sendChat.OnKeyDown("Enter"))
+
 			var content []h.H
 			content = append(content,
 				ui.BackToLobby(),
 				ui.StealthTitle("text-3xl font-bold"),
 				ui.PlayerInfo(g, myColor),
 				ui.StatusBanner(g, myColor, createRematch.OnClick()),
-				ui.BoardComponent(g, columnClick, myColor),
+				h.Div(h.Class("c4-game-area"), ui.BoardComponent(g, columnClick, myColor), chat),
 			)
 
 			if g.Status == game.StatusWaitingForPlayer {