feat: restore original UMO in respond stage and update send_message_to_user tool

Co-authored-by: Soulter <37870767+Soulter@users.noreply.github.com>

astrbot/core/astr_main_agent_resources.py

@@ -212,6 +212,10 @@ class SendMessageToUserTool(FunctionTool[AstrAgentContext]):
                         "required": ["type"],
                     },
                 },
+                "session": {
+                    "type": "string",
+                    "description": "Target session ID in format 'platform:type:session_id'. If not specified, sends to the current session.",
+                },
             },
             "required": ["messages"],
         }
@@ -253,7 +257,10 @@ class SendMessageToUserTool(FunctionTool[AstrAgentContext]):
     async def call(
         self, context: ContextWrapper[AstrAgentContext], **kwargs
     ) -> ToolExecResult:
-        session = kwargs.get("session") or context.context.event.unified_msg_origin
+        # In global context mode, default to original UMO if session not specified
+        original_umo = context.context.event.get_extra("original_umo")
+        default_session = original_umo or context.context.event.unified_msg_origin
+        session = kwargs.get("session") or default_session
         messages = kwargs.get("messages")
 
         if not isinstance(messages, list) or not messages:

astrbot/core/pipeline/respond/stage.py

@@ -169,6 +169,14 @@ class RespondStage(Stage):
             f"Prepare to send - {event.get_sender_name()}/{event.get_sender_id()}: {event._outline_chain(result.chain)}",
         )
 
+        # Restore original UMO before sending if in global context mode
+        original_umo = event.get_extra("original_umo")
+        if original_umo:
+            logger.debug(
+                f"Restoring original UMO before sending: {event.unified_msg_origin} -> {original_umo}"
+            )
+            event.unified_msg_origin = original_umo
+
         if result.result_content_type == ResultContentType.STREAMING_RESULT:
             if result.async_stream is None:
                 logger.warning("async_stream 为空，跳过发送。")