✨ feat(*): 添加 J519 实发重采样与 JSON 机型模型

* 新增 J519 实发采样器，按 8ms 周期生成 timing/jerk 诊断行并完成 rad->deg 转换
* 兼容层产物导出补充 speedRatio，规划编排补齐 smoothStartStopTiming 与日志透传
* 配置与机型加载切换到运行目录 JSON 模型，并补齐 7L 展开模型与相关单元测试

tests/Flyshot.Core.Tests/J519SendTrajectorySamplerTests.cs

@@ -0,0 +1,99 @@
+using Flyshot.Core.Planning.Sampling;
+
+namespace Flyshot.Core.Tests;
+
+/// <summary>
+/// 验证 J519 实发重采样器在离线导出和运行时下发之间保持一致的时间轴语义。
+/// </summary>
+public sealed class J519SendTrajectorySamplerTests
+{
+    /// <summary>
+    /// 验证 speed_ratio 只缩放轨迹时间，物理发送时间仍按固定伺服周期推进。
+    /// </summary>
+    [Fact]
+    public void SampleDenseJointTrajectory_MapsSendTimeToScaledTrajectoryTimeAndDegrees()
+    {
+        var denseTrajectory = new[]
+        {
+            new[] { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 },
+            new[] { 0.008, Math.PI / 2.0, 0.0, 0.0, 0.0, 0.0, 0.0 },
+            new[] { 0.016, Math.PI, 0.0, 0.0, 0.0, 0.0, 0.0 }
+        };
+
+        var samples = J519SendTrajectorySampler.SampleDenseJointTrajectory(
+            denseTrajectory,
+            durationSeconds: 0.016,
+            servoPeriodSeconds: 0.008,
+            speedRatio: 0.5);
+
+        Assert.Equal(5, samples.Count);
+        Assert.Equal(0, samples[0].SampleIndex);
+        Assert.Equal(0.0, samples[0].SendTime, precision: 6);
+        Assert.Equal(0.0, samples[0].TrajectoryTime, precision: 6);
+        Assert.Equal(0.0, samples[0].JointsDegrees[0], precision: 6);
+
+        Assert.Equal(1, samples[1].SampleIndex);
+        Assert.Equal(0.008, samples[1].SendTime, precision: 6);
+        Assert.Equal(0.004, samples[1].TrajectoryTime, precision: 6);
+        Assert.Equal(45.0, samples[1].JointsDegrees[0], precision: 6);
+
+        Assert.Equal(4, samples[^1].SampleIndex);
+        Assert.Equal(0.032, samples[^1].SendTime, precision: 6);
+        Assert.Equal(0.016, samples[^1].TrajectoryTime, precision: 6);
+        Assert.Equal(180.0, samples[^1].JointsDegrees[0], precision: 6);
+    }
+
+    /// <summary>
+    /// 验证空稠密轨迹会直接暴露为调用错误，避免生成无意义下发点。
+    /// </summary>
+    [Fact]
+    public void SampleDenseJointTrajectory_RejectsEmptyDenseTrajectory()
+    {
+        var exception = Assert.Throws<InvalidOperationException>(() =>
+            J519SendTrajectorySampler.SampleDenseJointTrajectory(
+                Array.Empty<IReadOnlyList<double>>(),
+                durationSeconds: 0.016,
+                servoPeriodSeconds: 0.008,
+                speedRatio: 1.0));
+
+        Assert.Contains("稠密关节轨迹为空", exception.Message);
+    }
+
+    /// <summary>
+    /// 验证非法 speed_ratio 会在公共入口统一拦截。
+    /// </summary>
+    [Theory]
+    [InlineData(0.0)]
+    [InlineData(double.NaN)]
+    [InlineData(double.PositiveInfinity)]
+    public void SampleDenseJointTrajectory_RejectsInvalidSpeedRatio(double speedRatio)
+    {
+        var denseTrajectory = new[]
+        {
+            new[] { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 }
+        };
+
+        Assert.Throws<ArgumentOutOfRangeException>(() =>
+            J519SendTrajectorySampler.SampleDenseJointTrajectory(
+                denseTrajectory,
+                durationSeconds: 0.0,
+                servoPeriodSeconds: 0.008,
+                speedRatio: speedRatio));
+    }
+
+    /// <summary>
+    /// 验证公共诊断行格式与既有 ActualSendTiming 文件保持一致。
+    /// </summary>
+    [Fact]
+    public void BuildTimingRow_UsesLegacyActualSendColumnOrder()
+    {
+        var row = J519SendTrajectorySampler.BuildTimingRow(new J519SendSample(
+            sampleIndex: 2,
+            sendTime: 0.016,
+            trajectoryTime: 0.008,
+            speedRatio: 0.5,
+            jointsDegrees: [90.0, 0.0, 0.0, 0.0, 0.0, 0.0]));
+
+        Assert.Equal([2.0, 0.016, 0.008, 0.5], row);
+    }
+}