update dask, gcsfs and xarray to 2026.x

[martibosch]

Description

update dask, gcsfs and xarray to 2026.x

Changes made:

• updated dask to ^2026.1.2
• updated gcsfs to ^2026.1.0`
• updated xarray to ^2026.02.0

Type of change

The change is not a bug fix, nor a new feature, nor a documention update. It can be breaking in terms of limiting compatibility with other libraries in a given environment, but there are no functionality changes within the updates, other than potential xarray warnings for concat/merge due to a new deprecation cycle in v2025.08.0.

Checklist

I have not added new tests nor updated the documentation because I do not think this applies here. Just FYI: ruff formats the tutorial notebook differently even though I did not change it.

• I have run poetry exec format to format my code
• I have added tests that prove my fix is effective or that my feature works
• I have updated the documentation accordingly
• All new and existing tests passed

Closes #

[martibosch]

for reference, my ultimate idea would be to use stationbench to compute station-based CRPS for ensemble forecasts, see an example application here.