Increase multidimensional testing for util module

[ajpotts]

Increase multidimensional testing for util module

[ajpotts]

✅ Functions that do have multi-dim tests

• utils.shape → has explicit 2-D test.
• Indirect: broadcast_dims is exercised by other N-D tests, but not directly.

❌ Functions with no multi-dim test coverage

• util.invert_permutation (only 1-D)
• util.broadcast_dims (no dedicated test)
• util._axis_validation / _integer_axis_validation (no dedicated test)
• util.map (only 1-D tested)
• util.copy (no explicit N-D test)

[ajpotts]

util.py:

invert_permutation, sparse_sum_help, and map need either guards (restrict to 1-D) or tests for N-D input.

Other functions are fine (either ndim-agnostic or already tested).

utils.py:

Already compliant: supports N-D and has tests for it.