fix: send proper hello response with version and audio_params

ESP32 expects full xiaozhi hello format including version and
audio_params, otherwise it disconnects and retries.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

relay.py

@@ -184,11 +184,18 @@ class Relay:
             msg_type = msg.get("type")
 
             if msg_type == "hello":
-                # Respond with hello ack
+                # Respond with proper hello — must match xiaozhi protocol
                 resp = {
                     "type": "hello",
-                    "session_id": "relay-session",
+                    "version": 1,
                     "transport": "websocket",
+                    "session_id": "relay-session",
+                    "audio_params": {
+                        "format": "opus",
+                        "sample_rate": ESP_SAMPLE_RATE,
+                        "channels": 1,
+                        "frame_duration": ESP_FRAME_MS,
+                    },
                 }
                 await self.ws.send(json.dumps(resp))
                 log.info(f"ESP32 hello: {msg.get('audio_params')}")