Fix dataset copy in coastline alteration and update to v1.5.1

[xylar]

Same bug as #714 in another place.

[xylar]

Testing

In the Polaris e3sm/init/qu240km/topo/cull test, I was seeing:

  File "/autofs/nccs-svm1_home1/xylar/e3sm_work/polaris/move-critical-passages-and-blockages-to-framework/pixi-env/.pixi/envs/default/lib/python3.14/site-packages/mpas_tools/ocean/coastline_alteration.py", line 178, in add_land_locked_cells_to_mask
    dsMask = xarray.Dataset(dsMask)
  File "/autofs/nccs-svm1_home1/xylar/e3sm_work/polaris/move-critical-passages-and-blockages-to-framework/pixi-env/.pixi/envs/default/lib/python3.14/site-packages/xarray/core/dataset.py", line 389, in __init__
    raise TypeError(
    ...<2 lines>...
    )
TypeError: Passing a Dataset as `data_vars` to the Dataset constructor is not supported. Use `ds.copy()` to create a copy of a Dataset.

With this fix, I'm no longer seeing that error.