tests fixes and some product advisories tunes ups

src/Policy/__Libraries/StellaOps.Policy/Gates/PolicyGateAbstractions.cs

@@ -1,4 +1,5 @@
 using System.Collections.Immutable;
+using StellaOps.Policy.Gates.Opa;
 using StellaOps.Policy.TrustLattice;
 
 namespace StellaOps.Policy.Gates;
@@ -34,6 +35,13 @@ public record PolicyGateContext
     /// Gates can add metadata here for later inspection.
     /// </summary>
     public Dictionary<string, string>? Metadata { get; init; }
+
+    /// <summary>
+    /// Optional supply chain evidence bundle for OPA policy evaluation.
+    /// When provided, OPA policies can access artifact metadata, SBOMs,
+    /// attestations, Rekor receipts, and VEX merge decisions.
+    /// </summary>
+    public OpaSupplyChainEvidence? SupplyChainEvidence { get; init; }
 }
 
 public sealed record GateResult