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/Attestor/StellaOps.Attestor/StellaOps.Attestor.Core.Tests/Validation/PredicateSchemaValidatorTests.cs

@@ -2,18 +2,15 @@ using System.Text.Json;
 using Microsoft.Extensions.Logging.Abstractions;
 using StellaOps.Attestor.Core.Validation;
 using Xunit;
-using Xunit.Abstractions;
 
 namespace StellaOps.Attestor.Core.Tests.Validation;
 
 public sealed class PredicateSchemaValidatorTests
 {
     private readonly PredicateSchemaValidator _validator;
-    private readonly ITestOutputHelper _output;
 
-    public PredicateSchemaValidatorTests(ITestOutputHelper output)
+    public PredicateSchemaValidatorTests()
     {
-        _output = output;
         _validator = new PredicateSchemaValidator(NullLogger<PredicateSchemaValidator>.Instance);
     }
 
@@ -23,15 +20,17 @@ public sealed class PredicateSchemaValidatorTests
         var assembly = typeof(PredicateSchemaValidator).Assembly;
         var resourceNames = assembly.GetManifestResourceNames();
         
-        _output.WriteLine($"Assembly: {assembly.FullName}");
-        _output.WriteLine($"Found {resourceNames.Length} resources:");
-        foreach (var name in resourceNames)
-        {
-            _output.WriteLine($"  - {name}");
-        }
-        
         Assert.Contains(resourceNames, n => n.Contains("vex-delta"));
         Assert.Contains(resourceNames, n => n.Contains("sbom-delta"));
+        
+        // Verify the exact resource names match what LoadSchemas expects
+        var resourcePrefix = "StellaOps.Attestor.Core.Schemas.";
+        Assert.Contains(resourceNames, n => n == resourcePrefix + "vex-delta.v1.schema.json");
+        Assert.Contains(resourceNames, n => n == resourcePrefix + "sbom-delta.v1.schema.json");
+        
+        // Verify we can load the stream directly
+        using var stream = assembly.GetManifestResourceStream(resourcePrefix + "vex-delta.v1.schema.json");
+        Assert.NotNull(stream);
     }
 
     [Fact]

src/Attestor/StellaOps.Attestor/StellaOps.Attestor.Core/Validation/PredicateSchemaValidator.cs

@@ -1,6 +1,7 @@
 using System.Text.Json;
 using Json.Schema;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
 
 namespace StellaOps.Attestor.Core.Validation;
 
@@ -52,21 +53,26 @@ public interface IPredicateSchemaValidator
 /// </summary>
 public sealed class PredicateSchemaValidator : IPredicateSchemaValidator
 {
-    private readonly IReadOnlyDictionary<string, JsonSchema> _schemas;
+    private static readonly Lazy<IReadOnlyDictionary<string, JsonSchema>> _lazySchemas = 
+        new(() => LoadSchemasInternal(NullLogger<PredicateSchemaValidator>.Instance), LazyThreadSafetyMode.ExecutionAndPublication);
+    
     private readonly ILogger<PredicateSchemaValidator> _logger;
 
     public PredicateSchemaValidator(ILogger<PredicateSchemaValidator> logger)
     {
         _logger = logger;
-        _schemas = LoadSchemas(_logger);
+        // Force schema loading on first access
+        _ = _lazySchemas.Value;
     }
 
+    private static IReadOnlyDictionary<string, JsonSchema> Schemas => _lazySchemas.Value;
+
     public ValidationResult Validate(string predicateType, JsonElement predicate)
     {
         // Normalize predicate type (handle both with and without stella.ops/ prefix)
         var normalizedType = NormalizePredicateType(predicateType);
 
-        if (!_schemas.TryGetValue(normalizedType, out var schema))
+        if (!Schemas.TryGetValue(normalizedType, out var schema))
         {
             _logger.LogDebug("No schema found for predicate type {PredicateType}, skipping validation", predicateType);
             return ValidationResult.Skip($"No schema for {predicateType}");
@@ -133,7 +139,7 @@ public sealed class PredicateSchemaValidator : IPredicateSchemaValidator
         return errors;
     }
 
-    private static IReadOnlyDictionary<string, JsonSchema> LoadSchemas(ILogger logger)
+    private static IReadOnlyDictionary<string, JsonSchema> LoadSchemasInternal(ILogger logger)
     {
         var schemas = new Dictionary<string, JsonSchema>(StringComparer.OrdinalIgnoreCase);