hull_grid.mirror_position gives the twin Position as grid_w - a - w, so an even-width footprint mirrors to its true
reflection and the cell lookup's tie rule no longer decides a mirror; the twin's object stands in the cell that Position
puts it in, so Package derives the same Position back. test_hull_grid pins the reflection on odd and even grids and
rows of 4 or more cells; smoke_mounts runs footprint widths 1 to 4 at every cell of an even and an odd grid, the
boundary tie, the armour and arc copy, the muzzle's local X, the centre-line threshold, the grid edge and the parent
check, and keeps a mirrored pair of two-cell footprints through Package and the validator. Every commit builds.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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