The grid and room engines write copper they never check. After a grid or
room run the result is now put through the exact engine's geometry (its
pads, fixed copper and keepouts; wires as boxes or slanted slabs; vias as
their pads) and the report gives the shorts and clearance violations, with
examples, instead of a blanket warning. --strict exits 3 when there are any;
by default the exit status stays 0 so the JAR drop-in contract holds.
The exact engine's static-copper setup moves into insert_static_copper so
both use it; exact runs are byte-identical before and after.