feat(mpsync): 实体位置广播（EntityMove）与客户端在线玩家显示；mesh 顶点池复用（性能与内存.md §2）

cmd/client/client_gl.go

@@ -57,6 +57,10 @@ type clientApp struct {
 	net *netclient.Client
 	log *logx.Logger
 
+	// 其他玩家位置（多人同步.md §3；渲染插值后置）
+	remoteMu      sync.Mutex
+	remotePlayers map[uint32][3]float64
+
 	meshBuilder *mesh.Builder
 
 	mu          sync.Mutex
@@ -90,6 +94,11 @@ func (a *clientApp) Tick(dt float64) {
 				} else {
 					a.screen = 1
 					a.rend.SetCursorMode(true)
+					a.hud.OnlineCount = func() int {
+						a.remoteMu.Lock()
+						defer a.remoteMu.Unlock()
+						return len(a.remotePlayers) + 1 // 含自己
+					}
 					a.logf("已连接服务器")
 				}
 			case "quit":
@@ -174,6 +183,7 @@ func (a *clientApp) Render() {
 	a.mu.Unlock()
 	for _, j := range pending {
 		a.rend.UploadChunk(j.cx, j.cz, j.m)
+		mesh.Release(j.m) // 上传完毕归还顶点池（性能与内存.md §2）
 	}
 
 	// 视图投影
@@ -365,19 +375,20 @@ func main() {
 	in := newInputState(rend.Window())
 
 	app := &clientApp{
-		sess:        sess,
-		rend:        rend,
-		reg:         reg,
-		in:          in,
-		uiR:         uiR,
-		hud:         hud,
-		titleScreen: titleScreen,
-		pauseScreen: pauseScreen,
-		log:         log,
-		meshBuilder: mesh.NewBuilder(reg, uvFn),
-		winW:        cfg.Client.WindowWidth,
-		winH:        cfg.Client.WindowHeight,
-		lastTime:    time.Now(),
+		sess:          sess,
+		rend:          rend,
+		reg:           reg,
+		in:            in,
+		uiR:           uiR,
+		hud:           hud,
+		titleScreen:   titleScreen,
+		pauseScreen:   pauseScreen,
+		log:           log,
+		remotePlayers: make(map[uint32][3]float64),
+		meshBuilder:   mesh.NewBuilder(reg, uvFn),
+		winW:          cfg.Client.WindowWidth,
+		winH:          cfg.Client.WindowHeight,
+		lastTime:      time.Now(),
 	}
 
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)