20,000 random trials found no boundary case. The chiral flip
(S-a vs a-S mod L) is a ring automorphism (negation) that preserves
the Sidon property. All chiral configs give the same Sidon result.
Proof: (a-S) mod L = -(S-a) mod L. The negation x→-x preserves
collision structure (x≡-x iff 2x≡0, same condition for both).
Implication: the chiral filter is trivial for CRT sums. It matters
for dual quaternion products (which involve multiplication, not
just addition). Next step: implement dual quaternion Sidon filter.
