Cube double-cover obstruction at (64,13,6,1,3)

Read notes/cube_double_cover_rank_obstruction_20261027.md for the hand proof.
Run: python src/verify_cube_double_cover_obstruction.py
Requires only Python standard library. No search solver or downloads.
The graph parameters remain open; only the specified induced structure is excluded.
The order32 fixture is the previously public monotone-transfer positive control.
