docs: revise lead-in UI spec with external/internal split and LayerType tagging

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Engine/NestProgress.cs

@@ -11,13 +11,38 @@ namespace OpenNest
         Remainder
     }
 
+    public class PhaseResult
+    {
+        public NestPhase Phase { get; set; }
+        public int PartCount { get; set; }
+        public long TimeMs { get; set; }
+
+        public PhaseResult(NestPhase phase, int partCount, long timeMs)
+        {
+            Phase = phase;
+            PartCount = partCount;
+            TimeMs = timeMs;
+        }
+    }
+
+    public class AngleResult
+    {
+        public double AngleDeg { get; set; }
+        public NestDirection Direction { get; set; }
+        public int PartCount { get; set; }
+    }
+
     public class NestProgress
     {
         public NestPhase Phase { get; set; }
         public int PlateNumber { get; set; }
         public int BestPartCount { get; set; }
         public double BestDensity { get; set; }
+        public double NestedWidth { get; set; }
+        public double NestedLength { get; set; }
+        public double NestedArea { get; set; }
         public double UsableRemnantArea { get; set; }
         public List<Part> BestParts { get; set; }
+        public string Description { get; set; }
     }
 }