The zone's gravity moves every ship, so an unpiloted scenario ship drifts
(about 14 m over 5 s at the test's spot) with nothing flying it. The rule is
"no agent steers it": the test now checks its movement and look inputs stay
untouched every tick, and that it still has no agent afterwards.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>