fv_frame_orthogonality_residual
===============================

.. py:function:: t3toolbox.backend.fv_operations.fv_frame_orthogonality_residual(frame)

   .. code-block:: python

      def fv_frame_orthogonality_residual(
              frame: typ.Tuple[
                  typ.Sequence[NDArray],  # up_tucker_cores
                  typ.Sequence[NDArray],  # down_tt_cores
                  typ.Sequence[NDArray],  # left_tt_cores
                  typ.Sequence[NDArray],  # right_tt_cores
              ],
      ) -> NDArray:  # shape = stack_shape (per stack element; scalar/0-d when unstacked)


   Max deviation from orthogonality of the four frame core families, **per stack element**.

   Checks each stacked block's gram against the identity:

   - up_tucker U_i (all i), outer/down D_i (all i),
   - left L_i (i=0..d-2), right R_i (i=1..d-1).

   The last left core and first right core are boundary remainders and are not checked. Returns the max
   absolute deviation reduced over the **non-stack** axes (shape ``stack_shape``); a caller thresholds it
   (``<= atol``) for a per-element boolean orthogonality test.