feat(io): add DetectTitleBlock option and TitleBlockEntityIds result property

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.IO/CadImportOptions.cs

@@ -16,6 +16,11 @@ namespace OpenNest.IO
         /// </summary>
         public bool DetectBends { get; set; } = true;
 
+        /// <summary>
+        /// When true, detects and identifies title block entities during import. Default true.
+        /// </summary>
+        public bool DetectTitleBlock { get; set; } = true;
+
         /// <summary>
         /// Override the drawing name. Null = filename without extension.
         /// </summary>

OpenNest.IO/CadImportResult.cs

@@ -45,5 +45,10 @@ namespace OpenNest.IO
         /// that need access to non-geometry entities (e.g., text annotations).
         /// </summary>
         public CadDocument Document { get; set; }
+
+        /// <summary>
+        /// GUIDs of entities identified as part of the title block during import.
+        /// </summary>
+        public HashSet<System.Guid> TitleBlockEntityIds { get; set; }
     }
 }