nx_research_orbit_gate.nx

nx_research_orbit_gate.nx -- the capstone of the dynamics thread: a 2-D gravitational orbit (inverse-square central force, a = -GM r / |r|^3) integrated in sovereign fixed-point (using our isqrt for |r|). THE canonical reason symplectic integrators exist: over many orbits the SYMPLECTIC leapfrog keeps the orbit BOUNDED and energy conserved, while naive forward-EULER pumps energy in and the orbit SPIRALS OUTWARD. Fixed-point precision trick: store velocity scaled by VS=2D, so the leapfrog half-kick v += a*dt/2 = a/(2D) becomes v_scaled += a EXACTLY (no truncation -- the dominant error source). Position step then divides by 2D*D. Verifier = energy conservation + orbit-radius bound; liar-kill = Euler's plausible orbit fails the bound the symplectic orbit holds. No float, deterministic. GREEN iff 6/6. license_tier: ORIGINAL