Add an SLSA Verification (SlsaVerification) step to an existing Harness pipeline to verify SLSA provenance attestations and optionally enforce OPA policy sets on provenance data. Supports CI and CD (Deployment) including CI-only pipelines — append a Deploy stage via Phase 3b when verifying before deploy. Supports Docker, ECR, GCR, GAR, ACR, HAR, and Local artifacts. Only works with existing pipelines. Use when asked to verify SLSA, enforce SLSA policies, add SLSA verification step, validate SLSA attestation, or gate deploy on SLSA provenance. Trigger phrases: enforce SLSA, SLSA verification, verify SLSA, SLSA policy enforcement, SlsaVerification, verify SLSA attestation, add SLSA verify step.