Complete batch 012 (golden set diff) and 013 (advisory chat), fix build errors

Sprints completed:
- SPRINT_20260110_012_* (golden set diff layer - 10 sprints)
- SPRINT_20260110_013_* (advisory chat - 4 sprints)

Build fixes applied:
- Fix namespace conflicts with Microsoft.Extensions.Options.Options.Create
- Fix VexDecisionReachabilityIntegrationTests API drift (major rewrite)
- Fix VexSchemaValidationTests FluentAssertions method name
- Fix FixChainGateIntegrationTests ambiguous type references
- Fix AdvisoryAI test files required properties and namespace aliases
- Add stub types for CveMappingController (ICveSymbolMappingService)
- Fix VerdictBuilderService static context issue

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.GoldenSet/Extensions/GoldenSetServiceCollectionExtensions.cs

@@ -0,0 +1,100 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
+using StellaOps.BinaryIndex.GoldenSet.Authoring;
+using StellaOps.BinaryIndex.GoldenSet.Authoring.Extractors;
+
+namespace StellaOps.BinaryIndex.GoldenSet;
+
+/// <summary>
+/// Extension methods for registering GoldenSet services.
+/// </summary>
+public static class GoldenSetServiceCollectionExtensions
+{
+    /// <summary>
+    /// Adds GoldenSet services to the dependency injection container.
+    /// </summary>
+    /// <param name="services">The service collection.</param>
+    /// <param name="configuration">The configuration.</param>
+    /// <returns>The service collection for chaining.</returns>
+    public static IServiceCollection AddGoldenSetServices(
+        this IServiceCollection services,
+        IConfiguration configuration)
+    {
+        ArgumentNullException.ThrowIfNull(services);
+        ArgumentNullException.ThrowIfNull(configuration);
+
+        // Configuration
+        services.AddOptions<GoldenSetOptions>()
+            .Bind(configuration.GetSection(GoldenSetOptions.SectionName))
+            .ValidateDataAnnotations()
+            .ValidateOnStart();
+
+        // Core services
+        services.TryAddSingleton<ISinkRegistry, SinkRegistry>();
+        services.TryAddSingleton<IGoldenSetValidator, GoldenSetValidator>();
+
+        // Memory cache (if not already registered)
+        services.AddMemoryCache();
+
+        return services;
+    }
+
+    /// <summary>
+    /// Adds GoldenSet authoring services to the dependency injection container.
+    /// </summary>
+    /// <param name="services">The service collection.</param>
+    /// <returns>The service collection for chaining.</returns>
+    public static IServiceCollection AddGoldenSetAuthoring(this IServiceCollection services)
+    {
+        ArgumentNullException.ThrowIfNull(services);
+
+        // Source extractors
+        services.TryAddEnumerable(ServiceDescriptor.Singleton<IGoldenSetSourceExtractor, NvdGoldenSetExtractor>());
+
+        // Composite extractor
+        services.TryAddSingleton<IGoldenSetExtractor, GoldenSetExtractor>();
+
+        // Upstream commit analyzer
+        services.TryAddSingleton<IUpstreamCommitAnalyzer, UpstreamCommitAnalyzer>();
+
+        // Enrichment service
+        services.TryAddScoped<IGoldenSetEnrichmentService, GoldenSetEnrichmentService>();
+
+        // Review workflow
+        services.TryAddScoped<IGoldenSetReviewService, GoldenSetReviewService>();
+
+        return services;
+    }
+
+    /// <summary>
+    /// Adds PostgreSQL-based GoldenSet storage to the dependency injection container.
+    /// </summary>
+    /// <param name="services">The service collection.</param>
+    /// <returns>The service collection for chaining.</returns>
+    public static IServiceCollection AddGoldenSetPostgresStorage(this IServiceCollection services)
+    {
+        ArgumentNullException.ThrowIfNull(services);
+
+        services.TryAddScoped<IGoldenSetStore, PostgresGoldenSetStore>();
+
+        return services;
+    }
+
+    /// <summary>
+    /// Adds a CVE validator implementation to the dependency injection container.
+    /// </summary>
+    /// <typeparam name="TValidator">The CVE validator implementation type.</typeparam>
+    /// <param name="services">The service collection.</param>
+    /// <returns>The service collection for chaining.</returns>
+    public static IServiceCollection AddGoldenSetCveValidator<TValidator>(this IServiceCollection services)
+        where TValidator : class, ICveValidator
+    {
+        ArgumentNullException.ThrowIfNull(services);
+
+        services.TryAddSingleton<ICveValidator, TValidator>();
+
+        return services;
+    }
+}