docs: document trajectory execution contracts

ClumsyPilot/ParkrobTrajplanner/TrajectoryExecution/PlanningCycleInput.cs

@@ -2,9 +2,12 @@ using System;
 
 namespace MultiWheelC.TrajectoryPlanning.EMPlanner;
 
-/// <summary>Caller-captured request and clock value for one rolling cycle.</summary>
+/// <summary>一次滚动周期的调用方冻结请求、身份和时钟值；构造后不读取外部状态。</summary>
 public sealed class PlanningCycleInput
 {
+    /// <summary>从一次 EM 规划请求和调用方时刻创建周期输入。</summary>
+    /// <param name="request">已冻结的 EM 请求；用于派生地图、路径、状态、上一轨迹和方向段身份。</param>
+    /// <param name="now">调用方提供的当前 <see cref="DateTimeOffset"/>；用于周期调度，不由协调器替换。</param>
     public PlanningCycleInput(EmPlanningRequest request, DateTimeOffset now)
     {
         Request = request ?? throw new ArgumentNullException(nameof(request));
@@ -13,12 +16,16 @@ public sealed class PlanningCycleInput
         ReplanPeriodSeconds = ReadReplanPeriod(request.Configuration);
     }
 
+    /// <summary>本周期消费的不可变 EM 规划请求快照。</summary>
     public EmPlanningRequest Request { get; }
 
+    /// <summary>从 <see cref="Request"/> 派生的完整版本身份，用于拒绝过期发布。</summary>
     public PlanningCycleIdentity Identity { get; }
 
+    /// <summary>调用方冻结的周期开始时刻。</summary>
     public DateTimeOffset Now { get; }
 
+    /// <summary>从请求配置读取的重规划周期，单位 s；无效配置回退为 0.20 s。</summary>
     public double ReplanPeriodSeconds { get; }
 
     private static double ReadReplanPeriod(EmPlannerConfiguration configuration)