The Shaper fits a hexagon's rotation by scoring 0, 90, 180 and 270
degrees, but a hexagon at 180 is the one at 0 (and 270 the one at 90):
those pairs score the same up to rounding, so the platform's atan2 picked
between them. FreeBSD's libm gave 270 where Linux gives 90, failing
tilted_rectangles_ellipses_and_hexagons_snap_to_their_angle_steps on the
FreeBSD build+test job. Candidates a whole number of periods from an
earlier one are now dropped. A new test reproduces the flip on Linux
with the old code (180 instead of 0 at tilt -9).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GQPh8UDgMyARR5Hat9UchC
