v0.2.1 - AIA GX Response Units

0.2.1 - AIA GX Response Units

Added

• Seven-channel AIA GX response regression coverage against a frozen SolarSoft
  IDL evenorm=1, chiantifix=1 response and time-dependent correction table.

Fixed

• AIA GX payloads now convert the response pixel area from arcsec^2 to
  steradians before folding emissivity. This restores the IDL per-pixel units,
  removes the former inverse-solid-angle scale error, and makes the
  evenorm_chiantifix path dimensionally compatible.
• An explicit GX platescale must be a solid angle. A dimensionless override
  is rejected before the response is folded.