Certified Computational Exclusion of Three-Hit Incongruent Restricted Disjoint Covering Systems at Length 108

This record provides a certificate-checked computational exclusion of three-hit incongruent restricted disjoint covering systems (IRDCS) on the interval [1,108]. For minimal modulus 2 <= p <= 17, the search is decomposed into 82 retained branches covering all 152 raw cases. The complete set of 82 branch-and-bound proof certificates is included and passes both the reference verifier and the fast verifier. The strict reflection quotient has 80 orbits; two retained branches are redundant reflected copies, so no cases are omitted. The case p >= 18 is excluded separately by an exact integer dual certificate with upper bound 106.0434714 < 108 and minimum integer slack 1. An independent C++ Algorithm X / dancing-links exhaustive computation provides an additional algorithmically independent cross-check of the UNSAT result for p = 2,...,17. The deposit contains the preprint, all 82 proof certificates, verification tools, manifests and SHA-256 hashes, verifier logs, the p >= 18 certificate and checker, the independent DLX audit, and scripts for reconstructing and independently re-verifying the complete proof package. The broader existence problem for three-hit IRDCS remains open. This work certifies nonexistence at n = 108; when combined with previously reported preliminary computational exclusions through n = 107, the reported computational frontier moves to n >= 109.