fix: compilation errors in Attestor and Policy modules

- Fix PredicateSchemaValidator to use static Lazy initialization
  avoiding JsonSchema.Net global registry conflicts in tests
- Add IContextPolicyGate interface for gates without MergeResult
- Rename ICveGate/IAttestationGate to avoid conflicts with IPolicyGate
- Add static Pass/Fail helper methods to GateResult record
- Unseal PolicyGateContext to allow ExtendedPolicyGateContext
- Add missing Type/Constraint properties to AuthorityScope and Principal
- Fix PolicyBundle to use ConditionDescription instead of Condition func
- Rename ExceptionResult to ExceptionCheckResult to avoid duplicate
- Rename GateResult static helper class to GateResultFactory
- Temporarily exclude 9 incomplete gate files with missing contracts
- Add AttestationContextExtensions for GetAttestation/GetVexSummary etc

All 216 Attestor.Core tests pass.

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

@@ -3,7 +3,7 @@ using StellaOps.Policy.TrustLattice;
 
 namespace StellaOps.Policy.Gates;
 
-public sealed record PolicyGateContext
+public record PolicyGateContext
 {
     public string Environment { get; init; } = "production";
     public int UnknownCount { get; init; }
@@ -42,6 +42,77 @@ public sealed record GateResult
     public required bool Passed { get; init; }
     public required string? Reason { get; init; }
     public required ImmutableDictionary<string, object> Details { get; init; }
+    
+    /// <summary>
+    /// Creates a passing gate result.
+    /// </summary>
+    public static GateResult Pass(string gateName, string reason, IEnumerable<string>? warnings = null)
+    {
+        var details = ImmutableDictionary<string, object>.Empty;
+        if (warnings != null)
+        {
+            var warningList = warnings.ToList();
+            if (warningList.Count > 0)
+            {
+                details = details.Add("warnings", warningList);
+            }
+        }
+        return new GateResult
+        {
+            GateName = gateName,
+            Passed = true,
+            Reason = reason,
+            Details = details
+        };
+    }
+    
+    /// <summary>
+    /// Creates a passing gate result with child gate results.
+    /// </summary>
+    public static GateResult Pass(string gateName, string reason, IReadOnlyList<GateResult>? childResults)
+    {
+        var details = childResults != null && childResults.Count > 0
+            ? ImmutableDictionary<string, object>.Empty.Add("childResults", childResults)
+            : ImmutableDictionary<string, object>.Empty;
+        return new GateResult
+        {
+            GateName = gateName,
+            Passed = true,
+            Reason = reason,
+            Details = details
+        };
+    }
+    
+    /// <summary>
+    /// Creates a failing gate result.
+    /// </summary>
+    public static GateResult Fail(string gateName, string reason, ImmutableDictionary<string, object>? details = null)
+    {
+        return new GateResult
+        {
+            GateName = gateName,
+            Passed = false,
+            Reason = reason,
+            Details = details ?? ImmutableDictionary<string, object>.Empty
+        };
+    }
+    
+    /// <summary>
+    /// Creates a failing gate result with child gate results.
+    /// </summary>
+    public static GateResult Fail(string gateName, string reason, IReadOnlyList<GateResult>? childResults)
+    {
+        var details = childResults != null && childResults.Count > 0
+            ? ImmutableDictionary<string, object>.Empty.Add("childResults", childResults)
+            : ImmutableDictionary<string, object>.Empty;
+        return new GateResult
+        {
+            GateName = gateName,
+            Passed = false,
+            Reason = reason,
+            Details = details
+        };
+    }
 }
 
 public sealed record GateEvaluationResult
@@ -51,6 +122,9 @@ public sealed record GateEvaluationResult
     public GateResult? FirstFailure => Results.FirstOrDefault(r => !r.Passed);
 }
 
+/// <summary>
+/// Policy gate interface for gates that require MergeResult.
+/// </summary>
 public interface IPolicyGate
 {
     Task<GateResult> EvaluateAsync(
@@ -59,6 +133,33 @@ public interface IPolicyGate
         CancellationToken ct = default);
 }
 
+/// <summary>
+/// Simplified policy gate interface for context-only evaluation.
+/// Used by attestation, runtime witness, and CVE gates that don't require MergeResult.
+/// </summary>
+public interface IContextPolicyGate
+{
+    /// <summary>
+    /// Gate identifier.
+    /// </summary>
+    string Id { get; }
+
+    /// <summary>
+    /// Display name for the gate.
+    /// </summary>
+    string DisplayName { get; }
+
+    /// <summary>
+    /// Description of what the gate checks.
+    /// </summary>
+    string Description { get; }
+
+    /// <summary>
+    /// Evaluates the gate against the given context.
+    /// </summary>
+    Task<GateResult> EvaluateAsync(PolicyGateContext context, CancellationToken ct = default);
+}
+
 public sealed record PolicyGateRegistryOptions
 {
     public bool StopOnFirstFailure { get; init; } = true;