block_sumsq_over_probes
=======================

.. py:function:: t3toolbox.backend.fitting.block_sumsq_over_probes(zz, n_w, has_order)

   .. code-block:: python

      def block_sumsq_over_probes(
              zz:         typ.Union[typ.Sequence[NDArray], NDArray],  # ragged len=d (elm [order]+W+C+(Ni,)) OR packed (d,)+[order]+W+C+(N,)
              n_w:        int,                    # number of leading W axes (unused; see block_sumsq_over_samples)
              has_order:  bool,
      ) -> NDArray:                               # (d, n_order) -- per-(mode, order) sum of squares


   Per-``(mode, order)`` sum-of-squares for the vector-output probe kinds -> a 2-D ``(d, n_order)``
   matrix (``d`` probe modes). Keeps the mode axis (and a leading order axis, if any) and sums the rest
   (``W`` + ``C`` + the free mode); **UNWEIGHTED**. **Mirrors** ``zz``'s packedness (like
   :py:func:`sumsq_over_probes`): a ragged ``len=d`` list stacks per-mode reductions; a **packed uniform**
   ``(d,)+[order]+W+C+(N,)`` array keeps the leading ``d`` (and order) axes and sums the rest -- the padded
   free mode ``N`` is a zeroed prefix (like ``sumsq``), so it contributes nothing. So the uniform probe
   kinds inherit this verbatim via ``dc.replace`` (no override needed).