Add XiaoZhi WebSocket server plugin for realtime voice conversations

[Copilot]

Implements XiaoZhi WebSocket protocol server as a BotSharp plugin to enable realtime voice conversations with xiaozhi-esp32 and compatible clients.

Implementation

Plugin Architecture

• XiaoZhiPlugin implements IBotSharpAppPlugin for automatic middleware registration
• XiaoZhiStreamMiddleware handles WebSocket connections at /xiaozhi/stream/{agentId}/{conversationId}
• Protocol models for client/server handshake and binary audio packets (v1/v2/v3)

Protocol Handling

• Client hello negotiation with version detection (1-3)
• Binary audio streaming: V1 (raw OPUS), V2 (16-byte header), V3 (4-byte header)
• JSON control messages (wake_word_detected, start_listening, stop_listening, abort_speaking)
• Direct WebSocket message handling—bypasses BotSharpRealtimeSession which only supports text

Integration

• Connects to IRealtimeHub for LLM realtime API conversations
• Base64 audio encoding for completer compatibility
• Conversation state persistence and routing

Configuration

{
  "XiaoZhi": {
    "EndpointPath": "/xiaozhi/stream",
    "DefaultProtocolVersion": 3,
    "AudioFormat": "opus",
    "SampleRate": 24000,
    "Channels": 1,
    "FrameDuration": 60
  }
}

Protocol Example

Client connects and sends hello:

{
  "type": "hello",
  "version": 3,
  "transport": "websocket",
  "audio_params": {
    "format": "opus",
    "sample_rate": 16000,
    "channels": 1,
    "frame_duration": 20
  }
}

Server responds with session:

{
  "type": "hello",
  "transport": "websocket",
  "session_id": "uuid",
  "audio_params": {
    "format": "opus",
    "sample_rate": 24000,
    "channels": 1,
    "frame_duration": 60
  }
}

Binary audio then flows bidirectionally using protocol-specific packet headers.

Compatibility

Works with xiaozhi-esp32, Verdure.Assistant, and py-xiaozhi clients. Reference implementation: xiaozhi-esp32-server.

Original prompt

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This section details on the original issue you should resolve

<issue_title>使用botsharp实现一个小智服务端</issue_title>
<issue_description>请你分析下面的.net的小智客户端
https://github.com/maker-community/Verdure.Assistant
和和官方的esp32版本的小智客户端
https://github.com/78/xiaozhi-esp32
以及第三方的python小智客户端
https://github.com/huangjunsen0406/py-xiaozhi
主要分析小智的通讯协议的逻辑，以websocket为准

再结合第三方实现的python服务端的实现
https://github.com/xinnan-tech/xiaozhi-esp32-server

结合botsharp的realtime的功能的实现
https://github.com/maker-community/BotSharp
在botsharp中实现一个插件，用来使用大模型实时api进行小智协议的适配，做到可以使用botsharp作为小智服务端的提供者。

注意事项：

1. 只新增插件单独实现小智服务端的功能
2. 功能尽量和botsharp的功能进行兼容
3. 以核心的对话作为实现目标，做到更换小智客户端ota地址就能够进行通话</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 使用botsharp实现一个小智服务端 #1

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