Three more constraint goals built on the same propagator-store
machinery as fd-neq:
fd-lt: x < y. Ground/ground compares; var/num filters domain;
var/var narrows x's domain to (< y-max) and y's to (> x-min).
fd-lte: ≤ variant.
fd-eq: x = y. Ground/ground checks. Var/num: requires num to be in
var's domain (or var unconstrained) before binding. Var/var: intersect
domains, narrow both, then unify the vars.
10 new tests: narrowing against ground, ordered-pair generation,
chained x<y<z determinism, domain-sharing, out-of-domain rejection.
603/603 cumulative (100/100 across the four CLP(FD) test files).
giles
c01ddc2b23