validate

Run both Arcgram self-checks in one call. A thin wrapper over Checkpoint (structure) and Reconcile (values): validate(diagram,{code}) runs Checkpoint always and Reconcile when code is supplied, then merges into one source-tagged result in the same {findings,summary,attestation,clean} contract. clean = checkpoint.clean && reconcile.clean. Adds no new check; marks, never blocks. Run after authoring or editing a…