Stage 02: EARTH_ORIENTATION — compute Earth's rotation at the epoch.
Produces sidereal time and an ECEF ↔ inertial rotation matrix with provenance.
@type t() :: %EphCore.SnapshotPipeline.EarthOrientation{ gast_degrees: float() | nil, gmst_degrees: float(), model: atom(), polar_motion_applied: boolean(), precession_nutation_applied: boolean(), rotation_matrix: AstroUtils.Matrix3.t() }
@spec resolve(term()) :: term()