Simplify codebase and fix Enter key on home page

- Enter key now triggers createGame action on home page
- Remove redundant setNickname action from home page
- Remove unused code: join channel, Leave(), Stop() methods
- Consolidate ID generation into game.GenerateID()
- Remove unused CreatedAt field from Game struct

main.go

@@ -1,9 +1,6 @@
 package main
 
 import (
-	"crypto/rand"
-	"encoding/hex"
-
 	"github.com/ryanhamamura/c4/game"
 	"github.com/ryanhamamura/c4/ui"
 	"github.com/ryanhamamura/via"
@@ -29,14 +26,6 @@ func main() {
 	v.Page("/", func(c *via.Context) {
 		nickname := c.Signal("")
 
-		setNickname := c.Action(func() {
-			name := nickname.String()
-			if name != "" {
-				c.Session().Set("nickname", name)
-				c.Sync()
-			}
-		})
-
 		createGame := c.Action(func() {
 			name := nickname.String()
 			if name == "" {
@@ -51,7 +40,7 @@ func main() {
 		c.View(func() h.H {
 			return ui.LobbyView(
 				nickname.Bind(),
-				setNickname.OnKeyDown("Enter"),
+				createGame.OnKeyDown("Enter"),
 				createGame.OnClick(),
 			)
 		})
@@ -66,8 +55,6 @@ func main() {
 		colSignal := c.Signal(0)
 
 		var gi *game.GameInstance
-		var player *game.Player
-		var playerJoined bool
 		var gameExists bool
 
 		// Look up game (may not exist during warmup or invalid ID)
@@ -75,6 +62,13 @@ func main() {
 			gi, gameExists = store.Get(gameID)
 		}
 
+		// Generate a stable player ID for this session
+		playerID := game.PlayerID(c.Session().GetString("player_id"))
+		if playerID == "" {
+			playerID = game.PlayerID(game.GenerateID(8))
+			c.Session().Set("player_id", string(playerID))
+		}
+
 		setNickname := c.Action(func() {
 			if gi == nil {
 				return
@@ -85,12 +79,13 @@ func main() {
 			}
 			c.Session().Set("nickname", name)
 
-			if !playerJoined {
-				player = &game.Player{
-					ID:       game.PlayerID(generatePlayerID()),
+			// Try to join if not already in game
+			if gi.GetPlayerColor(playerID) == 0 {
+				player := &game.Player{
+					ID:       playerID,
 					Nickname: name,
 				}
-				playerJoined = gi.Join(&game.PlayerSession{
+				gi.Join(&game.PlayerSession{
 					Player: player,
 					Sync:   c,
 				})
@@ -99,20 +94,25 @@ func main() {
 		})
 
 		dropPiece := c.Action(func() {
-			if gi == nil || player == nil {
+			if gi == nil {
+				return
+			}
+			myColor := gi.GetPlayerColor(playerID)
+			if myColor == 0 {
 				return
 			}
 			col := colSignal.Int()
-			gi.DropPiece(col, player.Color)
+			gi.DropPiece(col, myColor)
+			c.Sync()
 		})
 
 		// If nickname exists in session and game exists, join immediately
-		if gameExists && sessionNickname != "" {
-			player = &game.Player{
-				ID:       game.PlayerID(generatePlayerID()),
+		if gameExists && sessionNickname != "" && gi.GetPlayerColor(playerID) == 0 {
+			player := &game.Player{
+				ID:       playerID,
 				Nickname: sessionNickname,
 			}
-			playerJoined = gi.Join(&game.PlayerSession{
+			gi.Join(&game.PlayerSession{
 				Player: player,
 				Sync:   c,
 			})
@@ -125,8 +125,10 @@ func main() {
 				return h.Div()
 			}
 
-			// Need nickname first
-			if !playerJoined {
+			myColor := gi.GetPlayerColor(playerID)
+
+			// Need nickname first / not joined yet
+			if myColor == 0 {
 				return ui.NicknamePrompt(
 					nickname.Bind(),
 					setNickname.OnKeyDown("Enter"),
@@ -135,7 +137,6 @@ func main() {
 			}
 
 			g := gi.GetGame()
-			myColor := player.Color
 
 			// Create column click function
 			columnClick := func(col int) h.H {
@@ -164,12 +165,6 @@ func main() {
 	v.Start()
 }
 
-func generatePlayerID() string {
-	b := make([]byte, 8)
-	rand.Read(b)
-	return hex.EncodeToString(b)
-}
-
 const gameCSS = `
 	body { margin: 0; }