Fix build and code structure improvements. New but essential UI functionality. CI improvements. Documentation improvements. AI module improvements.

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

@@ -12,6 +12,28 @@ public sealed record PolicyGateContext
     public bool HasReachabilityProof { get; init; }
     public string? Severity { get; init; }
     public IReadOnlyCollection<string> ReasonCodes { get; init; } = Array.Empty<string>();
+
+    /// <summary>
+    /// Subgraph slice for reachability proof.
+    /// Required for high-severity findings when RequireSubgraphProofForHighSeverity is enabled.
+    /// </summary>
+    public SubgraphSlice? SubgraphSlice { get; init; }
+
+    /// <summary>
+    /// Subject key for Signals lookup.
+    /// </summary>
+    public string? SubjectKey { get; init; }
+
+    /// <summary>
+    /// CVE ID if applicable.
+    /// </summary>
+    public string? CveId { get; init; }
+
+    /// <summary>
+    /// Mutable metadata for audit trail.
+    /// Gates can add metadata here for later inspection.
+    /// </summary>
+    public Dictionary<string, string>? Metadata { get; init; }
 }
 
 public sealed record GateResult