feat: define path smoothing contracts

ClumsyPilot/ParkrobTrajplanner/PathSmoothing/Contracts/SmoothedPathPointSource.cs

@@ -0,0 +1,10 @@
+namespace MultiWheelC.TrajectoryPlanning.PathSmoothing;
+
+/// <summary>平滑路径点的来源。</summary>
+public enum SmoothedPathPointSource
+{
+    Anchor,
+    Interpolated,
+    GearSwitch,
+    CoarsePathFallback,
+}