feat(executor): add upstream disconnect handling for Codex WebSocket sessions

- Introduced `UpstreamDisconnectChan` for Codex WebSocket sessions to notify downstream connections of upstream disconnections.
- Implemented `notifyUpstreamDisconnect` to signal errors and close channels on disconnect events.
- Added integration tests to validate WebSocket session behavior on upstream disconnect.
- Updated OpenAI WebSocket response handlers to properly close connections upon upstream disconnect notifications.

internal/runtime/executor/codex_websockets_executor.go

@@ -76,6 +76,9 @@ type codexWebsocketSession struct {
 	activeCancel context.CancelFunc
 
 	readerConn *websocket.Conn
+
+	upstreamDisconnectOnce sync.Once
+	upstreamDisconnectCh   chan error
 }
 
 func NewCodexWebsocketsExecutor(cfg *config.Config) *CodexWebsocketsExecutor {
@@ -151,6 +154,22 @@ func (s *codexWebsocketSession) configureConn(conn *websocket.Conn) {
 	})
 }
 
+func (s *codexWebsocketSession) notifyUpstreamDisconnect(err error) {
+	if s == nil {
+		return
+	}
+	s.upstreamDisconnectOnce.Do(func() {
+		if s.upstreamDisconnectCh == nil {
+			return
+		}
+		select {
+		case s.upstreamDisconnectCh <- err:
+		default:
+		}
+		close(s.upstreamDisconnectCh)
+	})
+}
+
 func (e *CodexWebsocketsExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (resp cliproxyexecutor.Response, err error) {
 	if ctx == nil {
 		ctx = context.Background()
@@ -1221,11 +1240,22 @@ func (e *CodexWebsocketsExecutor) getOrCreateSession(sessionID string) *codexWeb
 	if sess, ok := store.sessions[sessionID]; ok && sess != nil {
 		return sess
 	}
-	sess := &codexWebsocketSession{sessionID: sessionID}
+	sess := &codexWebsocketSession{
+		sessionID:            sessionID,
+		upstreamDisconnectCh: make(chan error, 1),
+	}
 	store.sessions[sessionID] = sess
 	return sess
 }
 
+func (e *CodexWebsocketsExecutor) UpstreamDisconnectChan(sessionID string) <-chan error {
+	sess := e.getOrCreateSession(sessionID)
+	if sess == nil {
+		return nil
+	}
+	return sess.upstreamDisconnectCh
+}
+
 func (e *CodexWebsocketsExecutor) ensureUpstreamConn(ctx context.Context, auth *cliproxyauth.Auth, sess *codexWebsocketSession, authID string, wsURL string, headers http.Header) (*websocket.Conn, *http.Response, error) {
 	if sess == nil {
 		return e.dialCodexWebsocket(ctx, auth, wsURL, headers)
@@ -1354,6 +1384,7 @@ func (e *CodexWebsocketsExecutor) invalidateUpstreamConn(sess *codexWebsocketSes
 	sess.connMu.Unlock()
 
 	logCodexWebsocketDisconnected(sessionID, authID, wsURL, reason, err)
+	sess.notifyUpstreamDisconnect(err)
 	if errClose := conn.Close(); errClose != nil {
 		log.Errorf("codex websockets executor: close websocket error: %v", errClose)
 	}
@@ -1592,6 +1623,13 @@ func (e *CodexAutoExecutor) CloseExecutionSession(sessionID string) {
 	e.wsExec.CloseExecutionSession(sessionID)
 }
 
+func (e *CodexAutoExecutor) UpstreamDisconnectChan(sessionID string) <-chan error {
+	if e == nil || e.wsExec == nil {
+		return nil
+	}
+	return e.wsExec.UpstreamDisconnectChan(sessionID)
+}
+
 func codexWebsocketsEnabled(auth *cliproxyauth.Auth) bool {
 	if auth == nil {
 		return false