docs: document trajectory execution contracts

ClumsyPilot/ParkrobTrajplanner/TrajectoryExecution/TrajectoryExecutionState.cs

@@ -2,7 +2,7 @@ using System;
 
 namespace MultiWheelC.TrajectoryPlanning.EMPlanner;
 
-/// <summary>Immutable trajectory-execution outcome without controller or hardware coupling.</summary>
+/// <summary>不耦合控制器或硬件的不可变轨迹执行状态，组合选中点和换向状态机的安全语义。</summary>
 public sealed class TrajectoryExecutionState
 {
     internal TrajectoryExecutionState(EmTrajectoryPoint selectedPoint, GearSwitchStateUpdate gearSwitchUpdate)
@@ -19,14 +19,17 @@ public sealed class TrajectoryExecutionState
         Reason = gearSwitchUpdate.Reason;
     }
 
+    /// <summary>按调用方时刻选中或插值得到的轨迹点；位置为 m、航向为 rad、速度为 m/s。</summary>
     public EmTrajectoryPoint SelectedPoint { get; }
 
     public GearSwitchState GearSwitchState { get; }
 
+    /// <summary>是否要求保持零速度和零 yaw rate。</summary>
     public bool HoldZero { get; }
 
     public bool RequestDirectionChange { get; }
 
+    /// <summary>状态机是否允许跟随选中点的非零轨迹运动。</summary>
     public bool AllowsTrajectoryMotion { get; }
 
     public bool IsTrajectoryComplete { get; }