feat: add Unity project (Assets, ProjectSettings)

game/Assets/Scripts/Race/CheckpointTrigger.cs

@@ -0,0 +1,18 @@
+using UnityEngine;
+
+/// <summary>
+/// Attach to each checkpoint GameObject (which must have a trigger Collider).
+/// Set the checkpointIndex in the Inspector to match the checkpoint's position in the sequence.
+/// </summary>
+public class CheckpointTrigger : MonoBehaviour
+{
+    [Tooltip("Index in the CheckpointSystem.checkpoints array (0-based)")]
+    public int checkpointIndex = 0;
+
+    void OnTriggerEnter(Collider other)
+    {
+        // Only trigger for the local player (has PlayerController)
+        if (other.GetComponent<PlayerController>() == null) return;
+        CheckpointSystem.Instance?.OnLocalPlayerHitCheckpoint(checkpointIndex);
+    }
+}