2-level SP-GiST index on TLE data: SMA at L0, inclination at L1, with
query-time RAAN filter via J2 secular precession. New &? operator
(observer_window &? tle) returns true when a satellite might be visible
from a ground observer during a time window.
Index prunes by altitude band, inclination+footprint vs observer
latitude, and RAAN alignment against local sidereal time. Operator
class tle_spgist_ops is opt-in (not default), coexists with existing
GiST tle_ops. Equal-population picksplit with sqrt(n) bins.
