cmip7-prep (skeleton)

Quickstart:

1. Ensure you have a precomputed ESMF weights file: map_ne30pg3_to_1x1d_aave.nc.
2. Fill in cmor_dataset.json placeholders (experiment_id, etc.).
3. Export the CMIP7 Data Request v1.2.2 (CSV) as data_request_v1.2.2.csv.
4. poetry install
5. Prepare a variable, e.g., tas from TS: poetry run cmip7-prep prepare --var TS --realm Amon --dreq-export data_request_v1.2.2.csv --mapping-yaml cesm_to_cmip7.yaml --cmor-tables Tables --outdir out --in-files cam.h1.TS.ne30pg3.*.nc
6. Validate with PrePARE: PrePARE --table-path Tables out/*.nc