The Playground runs the formal invariant engines — M1 Axiom, M3 Structure, M5 Constraint, M6 Equivalence — against a real artifact and shows each verdict. This is not a checklist; each engine is a genuine invariant check on the same contract the runtime provides. Build a compliance evidence chain, validate it, then introduce a fault and watch the responsible engine catch it.
validate() contract and drop into these same slots at the runtime harvest.