BUG - SWAPI L3a proton-sw ISTP compliance

[jtniehof]

Description of the issue

Looking at imap_swapi_l3a_proton-sw_20260421_v021.cdf, there are several ISTP compliance failures with the work from #99

• proton_sw_bulk_velocity_rtn_sc and proton_sw_bulk_velocity_rtn_sun have a DEPEND_1 of rtn_label. rtn_label doesn't exist. The label should be LABL_PTR_1 and rtn_label should be a CDF_CHAR variable with Vr, Vt, Vn or similar. No DEPEND_1 is needed for simple axes anymore; see ISTP standard examples
• proton_sw_bulk_velocity_rtn_sc_covariance and proton_sw_bulk_velocity_rtn_sun_covariance need LABL_PTR for both dimensions.
• proton_sw_bulk_velocity_rtn_sc_covariance and proton_sw_bulk_velocity_rtn_sun_covariance have a lot of values under 0 and a VALIDMIN of 0; presumably the VALIDMIN needs to be updated
• Units on the new variables are IDL strings; they need to be updated to match IMAP nomenclature, e.g. km/s

Steps to reproduce the issue

No response

Expected vs Actual behavior

No response

Code Snippet (If applicable)

Code

Additional notes, affected areas, and suggested fixes

No response

[jtniehof]

@hafarooki I seem to have problems making assignments here; can you assign to yourself and address?

[hafarooki]

@jtniehof I don't seem to have the ability to assign myself

[jtniehof]

@hafarooki : yes, it looks like someone must have write access to have something assigned to you. Does it work for you to just proceed without assigning and open a PR?