fix(anim): Phase L.1c animate server-controlled chase

src/AcDream.Core/Physics/ServerControlledLocomotion.cs

@@ -0,0 +1,63 @@
+using System;
+using System.Numerics;
+
+namespace AcDream.Core.Physics;
+
+/// <summary>
+/// Chooses the visible locomotion cycle for server-controlled remotes whose
+/// UpdateMotion packet is a MoveToObject/MoveToPosition union rather than an
+/// InterpretedMotionState.
+///
+/// Retail references:
+/// <list type="bullet">
+/// <item><description>
+/// <c>MovementManager::PerformMovement</c> (0x00524440) dispatches movement
+/// types 6/7 into <c>MoveToManager::MoveToObject/MoveToPosition</c> instead
+/// of unpacking an InterpretedMotionState.
+/// </description></item>
+/// <item><description>
+/// <c>MovementParameters::UnPackNet</c> (0x0052AC50) shows MoveTo packets
+/// carry movement params + run rate, not a ForwardCommand field.
+/// </description></item>
+/// <item><description>
+/// ACE <c>MovementData.Write</c> uses the same movement type union; holtburger
+/// documents the matching <c>MovementType::MoveToPosition = 7</c>.
+/// </description></item>
+/// </list>
+/// </summary>
+public static class ServerControlledLocomotion
+{
+    public const float StopSpeed = 0.20f;
+    public const float RunThreshold = 1.25f;
+    public const float MinSpeedMod = 0.25f;
+    public const float MaxSpeedMod = 3.00f;
+
+    public static LocomotionCycle PlanFromVelocity(Vector3 worldVelocity)
+    {
+        float horizontalSpeed = MathF.Sqrt(
+            worldVelocity.X * worldVelocity.X +
+            worldVelocity.Y * worldVelocity.Y);
+
+        if (horizontalSpeed < StopSpeed)
+            return new LocomotionCycle(MotionCommand.Ready, 1f, false);
+
+        if (horizontalSpeed < RunThreshold)
+        {
+            float speedMod = Math.Clamp(
+                horizontalSpeed / MotionInterpreter.WalkAnimSpeed,
+                MinSpeedMod,
+                MaxSpeedMod);
+            return new LocomotionCycle(MotionCommand.WalkForward, speedMod, true);
+        }
+
+        return new LocomotionCycle(
+            MotionCommand.RunForward,
+            Math.Clamp(horizontalSpeed / MotionInterpreter.RunAnimSpeed, MinSpeedMod, MaxSpeedMod),
+            true);
+    }
+
+    public readonly record struct LocomotionCycle(
+        uint Motion,
+        float SpeedMod,
+        bool IsMoving);
+}