fix: aiocqhttp优先使用session_id发送消息 (#2623)

* fix: aiocqhttp优先使用session_id发送消息

当前aiocqhttp依赖raw_message来发送消息，raw_message为空时也无法有效回退到用group_id或user_id来发送，更符合逻辑的应该：优先使用session_id（group_id or user_id）,raw_message兜底

* Update aiocqhttp_message_event.py

* fix: validate session_id as integer and improve send_message docstring

---------

Co-authored-by: Soulter <905617992@qq.com>

astrbot/core/platform/sources/aiocqhttp/aiocqhttp_message_event.py

@@ -67,12 +67,19 @@ class AiocqhttpMessageEvent(AstrMessageEvent):
         session_id: str,
         messages: list[dict],
     ):
-        if event:
-            await bot.send(event=event, message=messages)
-        elif is_group:
+        # session_id 必须是纯数字字符串
+        session_id = int(session_id) if session_id.isdigit() else None
+
+        if is_group and isinstance(session_id, int):
             await bot.send_group_msg(group_id=session_id, message=messages)
-        else:
+        elif not is_group and isinstance(session_id, int):
             await bot.send_private_msg(user_id=session_id, message=messages)
+        elif isinstance(event, Event):  # 最后兜底
+            await bot.send(event=event, message=messages)
+        else:
+            raise ValueError(
+                f"无法发送消息：缺少有效的数字 session_id({session_id}) 或 event({event})"
+            )
 
     @classmethod
     async def send_message(
@@ -83,7 +90,15 @@ class AiocqhttpMessageEvent(AstrMessageEvent):
         is_group: bool = False,
         session_id: str = None,
     ):
-        """发送消息"""
+        """发送消息至 QQ 协议端（aiocqhttp）。
+
+        Args:
+            bot (CQHttp): aiocqhttp 机器人实例
+            message_chain (MessageChain): 要发送的消息链
+            event (Event | None, optional): aiocqhttp 事件对象.
+            is_group (bool, optional): 是否为群消息.
+            session_id (str | None, optional): 会话 ID（群号或 QQ 号
+        """
 
         # 转发消息、文件消息不能和普通消息混在一起发送
         send_one_by_one = any(
@@ -122,18 +137,15 @@ class AiocqhttpMessageEvent(AstrMessageEvent):
 
     async def send(self, message: MessageChain):
         """发送消息"""
-        event = self.message_obj.raw_message
-        assert isinstance(event, Event), "Event must be an instance of aiocqhttp.Event"
-        is_group = False
-        if self.get_group_id():
-            is_group = True
-            session_id = self.get_group_id()
-        else:
-            session_id = self.get_sender_id()
+        event = getattr(self.message_obj, "raw_message", None)
+
+        is_group = bool(self.get_group_id())
+        session_id = self.get_group_id() if is_group else self.get_sender_id()
+
         await self.send_message(
             bot=self.bot,
             message_chain=message,
-            event=event,
+            event=event,  # 不强制要求一定是 Event
             is_group=is_group,
             session_id=session_id,
         )