D10 (user decision 2026-10-13, keep the warning): a clamp footprint covering
the modeled program start (0,0) makes the first rapid of every posting attempt
cross it, and that warning has no exemption and no persisted bypass. Lock the
behavior in all four quadrants with a physical-footprint oracle and a mutation
red (skipping rapids that start inside a zone reddens exactly the four
origin-covering rows). Document the design in docs/post-verification.md.