Add Authority Advisory AI and API Lifecycle Configuration

- Introduced AuthorityAdvisoryAiOptions and related classes for managing advisory AI configurations, including remote inference options and tenant-specific settings.
- Added AuthorityApiLifecycleOptions to control API lifecycle settings, including legacy OAuth endpoint configurations.
- Implemented validation and normalization methods for both advisory AI and API lifecycle options to ensure proper configuration.
- Created AuthorityNotificationsOptions and its related classes for managing notification settings, including ack tokens, webhooks, and escalation options.
- Developed IssuerDirectoryClient and related models for interacting with the issuer directory service, including caching mechanisms and HTTP client configurations.
- Added support for dependency injection through ServiceCollectionExtensions for the Issuer Directory Client.
- Updated project file to include necessary package references for the new Issuer Directory Client library.

src/Scanner/__Libraries/StellaOps.Scanner.Surface.Validation/SurfaceValidationIssue.cs

@@ -0,0 +1,25 @@
+using System.Diagnostics.CodeAnalysis;
+
+namespace StellaOps.Scanner.Surface.Validation;
+
+/// <summary>
+/// Represents a single validation finding produced by a surface validator.
+/// </summary>
+public sealed record SurfaceValidationIssue(
+    string Code,
+    string Message,
+    SurfaceValidationSeverity Severity,
+    string? Hint = null)
+{
+    public static SurfaceValidationIssue Info(string code, string message, string? hint = null)
+        => new(code, message, SurfaceValidationSeverity.Info, hint);
+
+    public static SurfaceValidationIssue Warning(string code, string message, string? hint = null)
+        => new(code, message, SurfaceValidationSeverity.Warning, hint);
+
+    public static SurfaceValidationIssue Error(string code, string message, string? hint = null)
+        => new(code, message, SurfaceValidationSeverity.Error, hint);
+
+    [MemberNotNullWhen(true, nameof(Hint))]
+    public bool HasHint => !string.IsNullOrWhiteSpace(Hint);
+}