The nonlinear bound optimization can cross an unconditional bound such
as x² >= 0. Such bounds legitimately have no dependency witness, but
crossed-bound conflict construction asserted that a witness must
exist.\n\nAllow the null witness to participate as an empty dependency
and retain the asserted bound's explanation. This fixes the max_rev
regression without falling back to unknown.\n\nThe max_rev regression
and the full unit suite pass.
Copilot-Session: a8f87ede-b718-4fe9-9839-cc9eaaf9c3a7
c7b3b425e6