wombat_ic_generation: compatibility with older versions of FMS

[dougiesquire]

This PR includes some minor changes to types and attributes of files generated by SFe_climatology.py and regrid_forcing.py to allow them to be used by older versions of FMS (as used in ACCESS-OM2 and ACCESS-ESM1.6).

I also took the opportunity to get the output from SFe_climatology.py slightly closer to CF compliance. The output of cchecker.py is now at most Highly Recommended changes (previously this):

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                         IOOS Compliance Checker Report
                                 Version 5.3.0
                     Report generated 2025-09-17T00:42:26Z
                                    acdd:1.3
http://wiki.esipfed.org/index.php?title=Category:Attribute_Conventions_Dataset_Discovery
--------------------------------------------------------------------------------
                               Corrective Actions
CESM-MIMI_1980-2015_CAM4-6MEAN_MonthlyDep_Hamiltonetal2020_clim.nc has 5 potential issues


                               Highly Recommended
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Global Attributes
* Conventions does not contain 'ACDD-1.3'
* keywords not present
* summary not present

variable "SFe" missing the following attributes:
* coverage_content_type
* standard_name

variable "lat" missing the following attributes:
* long_name

variable "lon" missing the following attributes:
* long_name

variable "time" missing the following attributes:
* long_name

I've tested using files generated with these scripts in ACCESS-OM3 (new FMS) and ACCESS-ESM1.6 (old FMS).

[dougiesquire]

@anton-seaice, your CICE concatenation tests are failing (I think unrelated to changes in this PR)

[dougiesquire]

I've opened #84 about the failing tests

[anton-seaice]

This looks fine - I haven't tested anything but the changes don't look egregious. Normally i test for cf compliance (rather than acdd )

[dougiesquire]

Normally i test for cf compliance (rather than acdd )

Oops that was an accident

[dougiesquire]

For completeness:

--------------------------------------------------------------------------------
                         IOOS Compliance Checker Report
                                 Version 5.3.0
                     Report generated 2025-09-19T07:08:54Z
                                     cf:1.6
       http://cfconventions.org/cf-conventions/v1.6.0/cf-conventions.html
--------------------------------------------------------------------------------
                               Corrective Actions
CESM-MIMI_1980-2015_CAM4-6MEAN_MonthlyDep_Hamiltonetal2020_clim.nc has 4 potential issues


                                    Warnings
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§2.3 Naming Conventions
* global attribute Dust+Comb Dep should begin with a letter and be composed of letters, digits, and underscores
* global attribute Fire+Anth Dep should begin with a letter and be composed of letters, digits, and underscores

§2.6 Attributes
* §2.6.1 Conventions field is not present

§7.3 Cell Methods
* Climatology variable climatology_bounds may not contain attributes _FillValue or missing_value

§7.4 Climatological Statistics
* The "time: method within years/days over years/days" format is not correct in variable SFe.