refactor: remove custom deserializer, rely on SDK for Forward deserialization

- Remove _deserialize_message_chain from handler.py; use standard
  MessageChain.model_validate() (Forward handling fixed in SDK via
  langbot-app/langbot-plugin-sdk#38)
- Fix group_id type: use int instead of str for OneBot compatibility
- Add warning log when Forward message is used with non-group target

Author: RockChinQ

src/langbot/pkg/platform/sources/aiocqhttp.py

@@ -377,10 +377,15 @@ async def shutdown_trigger_placeholder():
     async def send_message(self, target_type: str, target_id: str, message: platform_message.MessageChain):
         # Check if message contains a Forward component
         forward_msg = message.get_first(platform_message.Forward)
-        if forward_msg and target_type == 'group':
-            # Send as merged forward message via OneBot API
-            await self._send_forward_message(int(target_id), forward_msg)
-            return
+        if forward_msg:
+            if target_type == 'group':
+                # Send as merged forward message via OneBot API
+                await self._send_forward_message(int(target_id), forward_msg)
+                return
+            else:
+                await self.logger.warning(
+                    f'Forward message is only supported for group targets, got target_type={target_type}. Falling through to normal send.'
+                )
 
         aiocq_msg = (await AiocqhttpMessageConverter.yiri2target(message))[0]
 
@@ -439,7 +444,7 @@ async def _send_forward_message(self, group_id: int, forward: platform_message.F
         # This matches the format used by GiveMeSetuPlugin
         bot_id = str(self.bot_account_id) if self.bot_account_id else '10000'
         payload = {
-            'group_id': str(group_id),
+            'group_id': group_id,
             'user_id': bot_id,  # Required by NapCat for display
             'messages': messages,
         }

src/langbot/pkg/plugin/handler.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import typing
-from typing import Any, List, Dict
+from typing import Any
 import base64
 import traceback
 
@@ -26,76 +26,6 @@
 from ..utils import constants
 
 
-def _deserialize_message_chain(data: List[Dict[str, Any]]) -> platform_message.MessageChain:
-    """Deserialize message chain with proper handling of Forward messages.
-
-    The default MessageChain.model_validate doesn't properly deserialize nested
-    MessageChain in ForwardMessageNode, causing data loss. This function handles
-    that case explicitly.
-    """
-    components = []
-    component_types = platform_message.MessageChain._get_component_types()
-
-    for item in data:
-        if not isinstance(item, dict) or 'type' not in item:
-            components.append(platform_message.Unknown(text=f'Invalid component: {item}'))
-            continue
-
-        comp_type = item['type']
-        if comp_type not in component_types:
-            components.append(platform_message.Unknown(text=f'Unknown type: {comp_type}'))
-            continue
-
-        comp_class = component_types[comp_type]
-
-        # Special handling for Forward messages
-        if comp_type == 'Forward':
-            node_list = []
-            for node_data in item.get('node_list', []):
-                # Recursively deserialize message_chain in each node
-                mc_data = node_data.get('message_chain', [])
-                if isinstance(mc_data, list):
-                    mc = _deserialize_message_chain(mc_data)
-                elif isinstance(mc_data, platform_message.MessageChain):
-                    mc = mc_data
-                else:
-                    mc = platform_message.MessageChain([])
-
-                node = platform_message.ForwardMessageNode(
-                    sender_id=node_data.get('sender_id', ''),
-                    sender_name=node_data.get('sender_name', ''),
-                    message_chain=mc,
-                    message_id=node_data.get('message_id', 0),
-                )
-                node_list.append(node)
-
-            display_data = item.get('display', {})
-            display = platform_message.ForwardMessageDiaplay(
-                title=display_data.get('title', 'Chat history'),
-                brief=display_data.get('brief', '[Chat history]'),
-                source=display_data.get('source', 'Chat history'),
-                preview=display_data.get('preview', []),
-                summary=display_data.get('summary', 'View forwarded messages'),
-            )
-
-            forward = platform_message.Forward(
-                display=display,
-                node_list=node_list,
-            )
-            components.append(forward)
-        else:
-            # For other component types, use default validation
-            # but handle Quote's nested MessageChain
-            if comp_type == 'Quote' and 'origin' in item:
-                origin_data = item['origin']
-                if isinstance(origin_data, list):
-                    item['origin'] = _deserialize_message_chain(origin_data)
-
-            components.append(comp_class.model_validate(item))
-
-    return platform_message.MessageChain(root=components)
-
-
 class RuntimeConnectionHandler(handler.Handler):
     """Runtime connection handler"""
 
@@ -350,7 +280,7 @@ async def send_message(data: dict[str, Any]) -> handler.ActionResponse:
             message_chain = data['message_chain']
 
             # Use custom deserializer that properly handles Forward messages
-            message_chain_obj = _deserialize_message_chain(message_chain)
+            message_chain_obj = platform_message.MessageChain.model_validate(message_chain)
 
             bot = await self.ap.platform_mgr.get_bot_by_uuid(bot_uuid)
             if bot is None: