Merge branch 'main' into fix/1535

- Add WebSocket heartbeat client for auto-reconnect
- Add js/heartbeat.js with heartbeat functionality
- Add script to index.html

Features:
1. Client sends heartbeat ping every 30 seconds
2. Server responds with pong + user count
3. Client auto-reconnects on missed 2 heartbeats
4. Reconnect preserves user position/identity
5. Exponential backoff for reconnection

Addresses issue #1535: feat: WebSocket heartbeat with auto-reconnect from client

Usage:
- Initialize: new NexusHeartbeat()
- Connect: heartbeat.connect('ws://localhost:8765')
- Update position: heartbeat.updatePosition(x, y, z)
- Get stats: heartbeat.getStats()

index.html

@@ -395,6 +395,7 @@
 <div id="memory-connections-panel" class="memory-connections-panel" style="display:none;" aria-label="Memory Connections Panel"></div>
 
 <script src="./boot.js"></script>
+<script src="./js/heartbeat.js"></script>
 <script src="./avatar-customization.js"></script>
 <script src="./lod-system.js"></script>
 <script>

js/heartbeat.js

@@ -0,0 +1,293 @@
+/**
+ * WebSocket Heartbeat Client for The Nexus
+ * Issue #1535: feat: WebSocket heartbeat with auto-reconnect from client
+ * 
+ * Provides:
+ * - Client sends heartbeat ping every 30s
+ * - Server responds with pong + user count
+ * - Client auto-reconnects on missed 2 heartbeats
+ * - Reconnect preserves user position/identity
+ */
+
+class NexusHeartbeat {
+    constructor(options = {}) {
+        this.heartbeatInterval = options.heartbeatInterval || 30000; // 30 seconds
+        this.maxMissedHeartbeats = options.maxMissedHeartbeats || 2;
+        this.reconnectDelay = options.reconnectDelay || 1000; // 1 second
+        this.maxReconnectDelay = options.maxReconnectDelay || 30000; // 30 seconds
+        
+        this.ws = null;
+        this.heartbeatTimer = null;
+        this.missedHeartbeats = 0;
+        this.isConnected = false;
+        this.userId = options.userId || this.generateUserId();
+        this.position = options.position || { x: 0, y: 0, z: 0 };
+        this.reconnectAttempts = 0;
+        
+        // Callbacks
+        this.onConnect = options.onConnect || (() => {});
+        this.onDisconnect = options.onDisconnect || (() => {});
+        this.onHeartbeat = options.onHeartbeat || (() => {});
+        this.onUserCount = options.onUserCount || (() => {});
+        this.onError = options.onError || console.error;
+        
+        // Bind methods
+        this.connect = this.connect.bind(this);
+        this.disconnect = this.disconnect.bind(this);
+        this.sendHeartbeat = this.sendHeartbeat.bind(this);
+        this.handleMessage = this.handleMessage.bind(this);
+        this.handleClose = this.handleClose.bind(this);
+        this.handleError = this.handleError.bind(this);
+    }
+    
+    generateUserId() {
+        return 'user_' + Math.random().toString(36).substr(2, 9);
+    }
+    
+    connect(url) {
+        if (this.ws && this.ws.readyState === WebSocket.OPEN) {
+            console.warn('Already connected');
+            return;
+        }
+        
+        this.url = url;
+        console.log(`Connecting to ${url}...`);
+        
+        try {
+            this.ws = new WebSocket(url);
+            this.ws.onopen = this.handleOpen.bind(this);
+            this.ws.onmessage = this.handleMessage;
+            this.ws.onclose = this.handleClose;
+            this.ws.onerror = this.handleError;
+        } catch (error) {
+            this.onError('Failed to create WebSocket:', error);
+            this.scheduleReconnect();
+        }
+    }
+    
+    disconnect() {
+        console.log('Disconnecting...');
+        
+        // Stop heartbeat
+        this.stopHeartbeat();
+        
+        // Close WebSocket
+        if (this.ws) {
+            this.ws.onclose = null; // Prevent reconnect on manual disconnect
+            this.ws.close(1000, 'Manual disconnect');
+            this.ws = null;
+        }
+        
+        this.isConnected = false;
+        this.missedHeartbeats = 0;
+        this.reconnectAttempts = 0;
+    }
+    
+    handleOpen() {
+        console.log('Connected to WebSocket');
+        this.isConnected = true;
+        this.missedHeartbeats = 0;
+        this.reconnectAttempts = 0;
+        
+        // Send reconnect message with user info
+        this.sendReconnect();
+        
+        // Start heartbeat
+        this.startHeartbeat();
+        
+        // Call connect callback
+        this.onConnect();
+    }
+    
+    handleMessage(event) {
+        try {
+            const data = JSON.parse(event.data);
+            
+            if (data.type === 'pong') {
+                // Reset missed heartbeats
+                this.missedHeartbeats = 0;
+                
+                // Update user count
+                if (data.user_count !== undefined) {
+                    this.onUserCount(data.user_count);
+                }
+                
+                // Call heartbeat callback
+                this.onHeartbeat(data);
+                
+                console.debug('Heartbeat pong received');
+            } else if (data.type === 'health') {
+                // Health check response
+                console.debug('Health check:', data);
+            } else {
+                // Regular message
+                console.debug('Message received:', data);
+            }
+        } catch (error) {
+            // Not JSON or parse error
+            console.debug('Non-JSON message received:', event.data);
+        }
+    }
+    
+    handleClose(event) {
+        console.log(`WebSocket closed: ${event.code} ${event.reason}`);
+        this.isConnected = false;
+        this.stopHeartbeat();
+        
+        // Call disconnect callback
+        this.onDisconnect(event);
+        
+        // Schedule reconnect if not manual disconnect
+        if (event.code !== 1000) {
+            this.scheduleReconnect();
+        }
+    }
+    
+    handleError(error) {
+        this.onError('WebSocket error:', error);
+    }
+    
+    startHeartbeat() {
+        if (this.heartbeatTimer) {
+            clearInterval(this.heartbeatTimer);
+        }
+        
+        console.log(`Starting heartbeat every ${this.heartbeatInterval / 1000}s`);
+        
+        this.heartbeatTimer = setInterval(() => {
+            this.sendHeartbeat();
+        }, this.heartbeatInterval);
+        
+        // Send initial heartbeat
+        this.sendHeartbeat();
+    }
+    
+    stopHeartbeat() {
+        if (this.heartbeatTimer) {
+            clearInterval(this.heartbeatTimer);
+            this.heartbeatTimer = null;
+        }
+    }
+    
+    sendHeartbeat() {
+        if (!this.isConnected || !this.ws || this.ws.readyState !== WebSocket.OPEN) {
+            console.warn('Cannot send heartbeat: not connected');
+            return;
+        }
+        
+        const heartbeat = {
+            type: 'heartbeat',
+            timestamp: Date.now(),
+            user_id: this.userId,
+            position: this.position
+        };
+        
+        try {
+            this.ws.send(JSON.stringify(heartbeat));
+            console.debug('Heartbeat sent');
+            
+            // Check for missed heartbeats
+            this.missedHeartbeats++;
+            if (this.missedHeartbeats > this.maxMissedHeartbeats) {
+                console.warn(`Missed ${this.missedHeartbeats} heartbeats, reconnecting...`);
+                this.ws.close(4000, 'Missed heartbeats');
+            }
+        } catch (error) {
+            this.onError('Failed to send heartbeat:', error);
+            this.ws.close(4001, 'Heartbeat send failed');
+        }
+    }
+    
+    sendReconnect() {
+        if (!this.isConnected || !this.ws || this.ws.readyState !== WebSocket.OPEN) {
+            console.warn('Cannot send reconnect: not connected');
+            return;
+        }
+        
+        const reconnect = {
+            type: 'reconnect',
+            timestamp: Date.now(),
+            user_id: this.userId,
+            position: this.position
+        };
+        
+        try {
+            this.ws.send(JSON.stringify(reconnect));
+            console.log('Reconnect message sent');
+        } catch (error) {
+            this.onError('Failed to send reconnect:', error);
+        }
+    }
+    
+    scheduleReconnect() {
+        if (this.reconnectAttempts >= 10) {
+            console.error('Max reconnect attempts reached');
+            return;
+        }
+        
+        // Exponential backoff
+        const delay = Math.min(
+            this.reconnectDelay * Math.pow(2, this.reconnectAttempts),
+            this.maxReconnectDelay
+        );
+        
+        console.log(`Reconnecting in ${delay / 1000}s (attempt ${this.reconnectAttempts + 1})...`);
+        
+        setTimeout(() => {
+            this.reconnectAttempts++;
+            this.connect(this.url);
+        }, delay);
+    }
+    
+    updatePosition(x, y, z) {
+        this.position = { x, y, z };
+        
+        // Send position update if connected
+        if (this.isConnected && this.ws && this.ws.readyState === WebSocket.OPEN) {
+            const update = {
+                type: 'position',
+                timestamp: Date.now(),
+                user_id: this.userId,
+                position: this.position
+            };
+            
+            try {
+                this.ws.send(JSON.stringify(update));
+            } catch (error) {
+                console.warn('Failed to send position update:', error);
+            }
+        }
+    }
+    
+    getUserId() {
+        return this.userId;
+    }
+    
+    getPosition() {
+        return { ...this.position };
+    }
+    
+    isConnectionActive() {
+        return this.isConnected && this.ws && this.ws.readyState === WebSocket.OPEN;
+    }
+    
+    getStats() {
+        return {
+            connected: this.isConnected,
+            userId: this.userId,
+            position: this.position,
+            missedHeartbeats: this.missedHeartbeats,
+            reconnectAttempts: this.reconnectAttempts
+        };
+    }
+}
+
+// Export for use in other modules
+if (typeof module !== 'undefined' && module.exports) {
+    module.exports = NexusHeartbeat;
+}
+
+// Global instance for browser use
+if (typeof window !== 'undefined') {
+    window.NexusHeartbeat = NexusHeartbeat;
+}