Captures the three non-negotiable invariants (DRC-clean output, exact integer
geometry, determinism), the engine matrix, the reference/ GPL rule, the JAR
oracle strategy, and the lessons that cost real debugging: KiCad's /*52 net
names, exact clearance being load-bearing, shove not being a densifier, and the
falsifiable-fixture bar for any density claim.
Force-added past the global ignore: this is a private repo and the file is
excluded from the sdist, so it never reaches PyPI.
