fix(llm-bridge): mem source & reducer close mem conn (#1023)

Fix unexpected `panic: unimplemented` when LRU closes the reducer.

Author: woorui

pkg/bridge/ai/reducer.go

@@ -39,8 +39,11 @@ func (m *memSource) Connect() error {
 	return m.conn.Handshake(hf)
 }
 
+func (m *memSource) Close() error {
+	return m.conn.CloseWithError("llm bridge source closed")
+}
+
 func (m *memSource) Write(_ uint32, _ []byte) error  { panic("unimplemented") }
-func (m *memSource) Close() error                    { panic("unimplemented") }
 func (m *memSource) SetErrorHandler(_ func(_ error)) { panic("unimplemented") }
 
 func (m *memSource) WriteWithTarget(tag uint32, data []byte, target string) error {
@@ -76,10 +79,6 @@ func NewReducer(conn *mem.FrameConn, cred *auth.Credential) yomo.StreamFunction
 	}
 }
 
-func (m *memStreamFunction) Close() error {
-	return nil
-}
-
 func (m *memStreamFunction) Connect() error {
 	hf := &frame.HandshakeFrame{
 		Name:            "fc-reducer",
@@ -114,6 +113,10 @@ func (m *memStreamFunction) Connect() error {
 	return nil
 }
 
+func (m *memStreamFunction) Close() error {
+	return m.conn.CloseWithError("llm bridge reducer closed")
+}
+
 func (m *memStreamFunction) onDataFrame(dataFrame *frame.DataFrame) {
 	serverlessCtx := serverless.NewContext(m.conn, dataFrame.Tag, core.NewMetadata(m.id, id.New()), dataFrame.Payload)
 	m.handler(serverlessCtx)