t3_broadcast_to_common_stack
============================

.. py:function:: t3toolbox.backend.t3_operations.t3_broadcast_to_common_stack(tucker_cores, tt_cores)

   .. code-block:: python

      def t3_broadcast_to_common_stack(
              tucker_cores: typ.Sequence[NDArray],  # each shape = stack_i + (n, N)
              tt_cores:     typ.Sequence[NDArray],  # each shape = stack_i + (rL, n, rR)
      ) -> typ.Tuple[
          typ.Tuple[NDArray, ...],  # tucker_cores, each shape = stack + (n, N)
          typ.Tuple[NDArray, ...],  # tt_cores,     each shape = stack + (rL, n, rR)
      ]:


   Broadcast every core of a T3 up to the common (broadcast) stack of all its cores.

   Cores may carry different but broadcastable leading stack axes -- e.g. a single-core-replacement
   term (``fv_to_t3``) or a tangent term mixes a V+G-stacked variation core with G-stacked frame
   cores (the shared base point replicated over the tangent stack V). Returns the cores all stacked
   at the common ``np.broadcast_shapes`` stack, so the result is a valid uniform-stack T3. A no-op
   when every core already shares one stack.