Certified Computational Evidence for D_mono(18) = 27

This archive contains the complete computational certificate and independent reproduction evidence supporting the finite exact value D_mono(18) = 27 for the checkerboard-restricted no-three-in-line problem at n = 18. It includes the exact 27-point construction; geometry, CNF, partition, and BDD source code; 203 regenerated CNF cores and 203 DRAT proofs; the drat-trim checker identity; manifests; SHA-256 inventories; environment capture; logs; and independent reproduction reports. All 203 regenerated proof pairs were checked successfully. The result is not the classical unrestricted D(18), not a theorem for general n, and not a proof-assistant or LRAT formalization. Final archive SHA-256: bb8425bcae2988c63d7b54a5e395ee839e520a8b0d01bef49ce40f5eae64307e.