v0.2.0

Minor bodies: comets and numbered asteroids at acquisition time

MPC element sets (CometEls.txt + MPCORB) propagate with two-body
mechanics — elliptic and hyperbolic Kepler plus Barker's parabolic
case — against the JPL approximate Earth ephemeris, with a light-time
iteration. These objects move arcminutes to degrees per day, so
`solve --minor-bodies elements.bin --time <ISO>` (or the FITS DATE-OBS
header) evaluates positions at the exact acquisition time and lists
what is in the footprint with estimated magnitudes.

Validation: (1) Ceres lands 16 arcsec from the JPL Horizons geocentric
position; C/2025 A6 (Lemmon) propagated to a real image's capture night
lands 0.25 deg from the solved frame center — the comet labels itself.
New: download-data mpc, build-data minor-bodies (asteroid H cutoff,
default 16), the SEIZAMB1 element format, and a Windows x86_64 zip in
the release workflow.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>