docs: document smoothing processing core

ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Processing/PreparedPath.cs

@@ -8,6 +8,7 @@ namespace MultiWheelC.TrajectoryPlanning.PathSmoothing.Processing;
 public sealed class PreparedPath
 {
     /// <summary>创建不可变预处理路径。</summary>
+    /// <param name="segments">按原始行驶顺序排列的非空方向段集合；构造后会复制为只读快照。</param>
     public PreparedPath(IReadOnlyList<PreparedDirectionSegment> segments)
     {
         if (segments == null || segments.Count == 0)
@@ -22,10 +23,10 @@ public sealed class PreparedPath
         Points = Flatten(Segments);
     }
 
-    /// <summary>按原始前进/倒车拓扑排列的方向段。</summary>
+    /// <summary>按原始前进/倒车拓扑排列的 <see cref="PreparedDirectionSegment"/> 只读集合。</summary>
     public IReadOnlyList<PreparedDirectionSegment> Segments { get; }
 
-    /// <summary>将所有方向段顺序拼接后的点；换向重复点保留两次。</summary>
+    /// <summary>将所有方向段顺序拼接后的 <see cref="SmoothingPoint2D"/> 只读集合；换向重复点保留两次。</summary>
     public IReadOnlyList<SmoothingPoint2D> Points { get; }
 
     private static IReadOnlyList<T> CopyReadOnly<T>(IReadOnlyList<T> source)