message: fix ek.make_opaque for AD arrays
diff: @@ -2433,7 +2433,7 @@ def make_opaque(*args):
  for i in range(len(a)):
  make_opaque(a.entry_ref_(i))
  elif _ek.is_diff_array_v(t):
  - make_opaque(a.detach_())
  + make_opaque(a.detach_ref_())
  elif _ek.is_tensor_v(t):
  make_opaque(a.array)
  elif _ek.is_jit_array_v(t):
  