Corner Itineraries and Resonance of ASM Superpromotion

We construct an explicit binary-word factor of Striker-Williams superpromotion on alternating sign matrices of order n. The membership indicator of a specified corner of the ASM poset returns after 3n-2 steps. Its itinerary of that length therefore intertwines superpromotion with cyclic rotation. For n >= 3, rotation on the image has effective order exactly 3n-2; the n = 2 exception has effective order 2. The proof combines a face-stratum bijection with time-shift recombination on the tetrahedral poset and does not enumerate full orbits. Evaluation takes O(n^4) elementary toggle tests. This is a complete dynamical corner-factor theorem associated with AIM Problem 2.7 and UnsolvedMath record AIM-OTHER-0011. It is not a static noncrossing model, an independent characterization of all image words, or the proposed order-polytope projection. The whole source record is not counted as closed, and no full-action periodicity is asserted. The ASM poset, superpromotion, empty/full-ideal orbit and general resonance framework are credited prior work. The release contains a six-page English manuscript, LaTeX source, exact standard-library Python regression checks and a verification report. The arbitrary-n proof is separate from finite computational evidence. This AI-assisted, originating-researcher self-audited preprint is unrefereed; independent review, proof-assistant formalization and absolute priority are not claimed. Novelty remains undetermined after a bounded primary-source search.