feat(acp): relay skeleton (subscribe/unsubscribe/fanout/close) + supervisor.GetRelay

internal/acp/supervisor.go

@@ -83,6 +83,7 @@ type Process struct {
 	Stdin  io.WriteCloser
 	Stdout io.ReadCloser
 	Stderr io.ReadCloser
+	Relay  *Relay
 
 	StderrBuf  *stderrRing  // 排障 ring buffer
 	StartedAt  time.Time
@@ -121,6 +122,16 @@ func (r *stderrRing) Tail(maxBytes int) string {
 	return out
 }
 
-// Relay field + GetRelay method added in Task D7 when Relay type is wired.
+// GetRelay returns the relay for an active session, or nil if not running.
+// WS handler 用此判断是否进 live 模式。
+func (s *Supervisor) GetRelay(sid uuid.UUID) *Relay {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	p, ok := s.procs[sid]
+	if !ok {
+		return nil
+	}
+	return p.Relay
+}
 
 // Spawn / Kill / ShutdownAll / monitorProcess / handshake are implemented in subsequent tasks (E2).