v0.8.1

v0.8.1 — non-grav covariance everywhere, chronological outputs, linkable macOS engine

Fixes

• The fitted non-grav 3σ covariance from orbit determination now
  reaches every Python forward model (propagate, ephemeris generation,
  impact probabilities, B-planes) instead of being silently dropped at
  the binding — propagated σ for non-grav-solved orbits was understated
  (~2,800 km in quadrature at Apophis's 2029 close approach). The Rust
  channel always forwarded it; the channels now agree.
• Observing nights for western observatories are stamped with the local
  observing night instead of the UTC date (signed-longitude fold).
• Observation sensitivity rows populate whenever STM tracing is
  requested — no input covariance needed for the Jacobian; only the
  projected sky covariance still requires one.
• The released macOS libempyrean.dylib carries an @rpath install name;
  C consumers can link the tarball as shipped with -Wl,-rpath.

Behavior

• Propagation output is in ascending epoch order, always — positional
  pairing against an ascending, duplicate-free request grid is exact.
  Ephemeris entries keep their observer-input order (engine-tested).
• Python-extension orbit marshaling is drop-proofed behind a single
  exhaustive construction chokepoint, with the contract suite
  exercising the non-grav covariance input channel end to end.

Binds empyrean-core v0.8.2 (villeneuve v1.18.1, scott v1.13.3).