feat: add smoothing algorithm retry runner

ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Algorithms/IPathSmoother.cs

@@ -0,0 +1,14 @@
+using System.Threading;
+
+namespace MultiWheelC.TrajectoryPlanning.PathSmoothing.Algorithms;
+
+/// <summary>单一平滑方法生成原始几何候选的内部契约。</summary>
+internal interface IPathSmoother
+{
+    SmoothingMethod Method { get; }
+
+    SmoothingCandidate Smooth(
+        SmoothingAlgorithmInput input,
+        double effectiveStrength,
+        CancellationToken cancellationToken);
+}