feat: support quoted message headers

docs/IM-前后端对接文档.md

@@ -343,6 +343,7 @@ X-MeetingIM-APIKey: <预置的普通 API Key>
 | 类型 | 客户端发送 | 服务端返回/下行示例 |
 | --- | --- | --- |
 | 文本消息 | `{"pub":{"id":"pub-text-1","topic":"p2p...","noecho":false,"head":{"mime":"application/json","x-im-schema":1,"x-im-type":"text","x-im-client-mid":"mid_1"},"content":{"text":"你好"}}}` | 发送方收到 `{"ctrl":{"id":"pub-text-1","code":202,"text":"accepted","params":{"seq":12}}}`；订阅者收到 `{"data":{"topic":"p2p...","seq":12,"from":"usr...","head":{"x-im-type":"text","x-im-client-mid":"mid_1"},"content":{"text":"你好"}}}` |
+| 引用回复文本 | `{"pub":{"id":"pub-reply-1","topic":"p2p...","head":{"mime":"application/json","x-im-schema":1,"x-im-type":"text","x-im-client-mid":"mid_reply_1","x-im-reply":{"seq":128,"type":"text","text":"今天晚上一起吃饭吗？","from":"usr..."}},"content":{"text":"好啊"}}}` | `x-im-reply` 必须保留在 `head` 中；服务端不解析业务语义，入库、实时下行和历史读取均原样返回 |
 | 图片消息 | `{"pub":{"id":"pub-img-1","topic":"grp...","head":{"mime":"application/json","x-im-schema":1,"x-im-type":"image","x-im-client-mid":"mid_img_1"},"content":{"file_id":"file_img","thumbnail_file_id":"file_thumb","name":"a.jpg","size":12345,"mime":"image/jpeg","width":1080,"height":720}}}` | `{"ctrl":{"id":"pub-img-1","code":202,"params":{"seq":13}}}` |
 | 语音消息 | `{"pub":{"id":"pub-voice-1","topic":"grp...","head":{"mime":"application/json","x-im-schema":1,"x-im-type":"voice","x-im-client-mid":"mid_voice_1"},"content":{"file_id":"file_voice","duration_ms":8000,"size":4096,"mime":"audio/aac","waveform":[1,3,5,2]}}}` | `{"ctrl":{"id":"pub-voice-1","code":202,"params":{"seq":14}}}` |
 | 文件消息 | `{"pub":{"id":"pub-file-1","topic":"grp...","head":{"mime":"application/json","x-im-schema":1,"x-im-type":"file","x-im-client-mid":"mid_file_1"},"content":{"file_id":"file_pdf","name":"方案.pdf","size":102400,"mime":"application/pdf","extension":"pdf","checksum":"sha256:..."}}}` | `{"ctrl":{"id":"pub-file-1","code":202,"params":{"seq":15}}}` |
@@ -647,6 +648,8 @@ X-MeetingIM-APIKey: <预置的普通 API Key>
 
 `x-im-client-mid` 由客户端生成 ULID/UUID，作用域为“租户 + 发送人”，断线重试必须复用；服务端目标实现应返回第一次写入的同一 `seq`。未知 `x-im-type` 显示“暂不支持的消息”，不得崩溃或删除消息。
 
+引用回复使用 `head.x-im-reply` 承载客户端生成的轻量快照，字段为 `seq:number`、`type:string`、`text:string`，可选 `from:string`。该对象必须放在 `head`，不能放入 `content`；服务端只负责把未知 `head` 字段随消息存储、实时转发、历史拉取和 HTTP 查询一起原样返回，不对被引用消息做二次查询或语义校验。客户端兼容历史服务端将 `x-im-reply` 作为 JSON 字符串返回的情况，但新版本客户端发送时必须使用 JSON 对象。
+
 消息类型首版固定为：`text`、`image`、`video`、`voice`、`file`、`contact_card`、`link`、`forward_bundle`、`call`、`system_notice`、`system_action`、`system_event`。自定义表情启用后追加 `sticker`。媒体内容只保存 `file_id`、文件元数据和缩略图 ID，不保存可长期绕过鉴权的公共 URL。`system_notice` 和 `system_action` 只能由服务端生成，普通用户构造后发送必须被服务端拒绝。
 
 ### 0.7 HTTP 幂等、重试和安全