The PR's principal-axis math now lives in the codec's transform_ellipse
(8464e0a), which explode, INSERT and every other codec path share.
transform_ellipse_geometry delegates to it for the block-cache tangent,
and the entity goes back through apply_standard_entity_transform, with
MIRROR delegated to the codec's apply_mirror: the old closure reflected
only the centre and major axis, leaving mirrored arcs on the wrong side,
and the PR's version turned the normal to -Z. The mirror test now checks
the kept +Z normal and the negated parameters.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>