Migration from sgl2020

Version 0.2 is a direct break and uses the new distribution name dafmit-aeromag with the import namespace dafmit_aeromag. The old sgl2020 package and its stateful query builder are not compatibility aliases.

Older pattern	New pattern
from sgl2020 import Sgl2020	from dafmit_aeromag import Dataset, Selection
Sgl2020().line("1002.01").source(...).take()	Dataset().read(Selection(1002, lines="1002.01"), columns=[...])
Hand-maintained 2020 descriptions	Dataset().flights(), .fields(), and .segments()
Implicit cache and moving DOI target	Fixed v3 manifest plus configurable data_dir

The new API makes flight scope explicit, supports 2021 files, and exposes normalized and raw output modes. Existing downstream code should migrate its imports and make its selected columns explicit.