Lift xarray pin

[Zeitsperre]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes issue #xyz
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• HISTORY.rst has been updated (with summary of main changes)

What kind of change does this PR introduce?:

• Lifts the xarray pin for compatible xesmf
• Raises the base pandas version
• Adjusts the Makefile to work better with tox
• Adds a default output engine to ops outputs
• Removes several obsolete pytest.mark.xfail markers

Does this PR introduce a breaking change?:

Somewhat. This PR adds a default output engine for nc/netcdf files (h5netcdf). This works better for most cases (i.e. better thread safety), except for instances where the metadata contains badly-encoded strings.

Other information:

pydata/xarray#7794
pydata/xarray#8821

[coveralls]

Pull Request Test Coverage Report for Build 15883479025

Details

• 7 of 7 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 87.024%

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Totals
Change from base Build 15824994976:	0.02%
Covered Lines:	3105
Relevant Lines:	3568

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💛 - Coveralls

[cehbrecht]

@Zeitsperre does regridding work now with the latest xesmf/xarray version?

[Zeitsperre]

@cehbrecht As of release 2025.6, yes, everything should work properly. I've removed a bunch of the skip markers and everything seems to be working as intended.