CHRONOS: a reusable exact-certification tool for step constructions (C1)

Certified Hyra's leader as a PROVEN upper bound: C1 <= 1.5028503020710078765191888 (exact rational, no floating point on the certified path). This ties Hyra's existing leader -- it is an exact evaluation of that vector, not an improvement. The point is a reusable tool: a short lemma shows that for a step function the autoconvolution is piecewise linear with breakpoints on the half-grid, so the board's discrete max equals the continuum supremum exactly (zero discretization loss). That turns any step construction here into a theorem-grade bound in seconds. Full method + stdlib-only scripts: DOI 10.5281/zenodo.21194862 -- happy to help anyone certify their own vector.