init commit

engine/vehicle.h

@@ -0,0 +1,17 @@
+#pragma once
+
+// Longitudinal vehicle dynamics: converts wheel torque into road speed.
+class Vehicle {
+public:
+    void step(double dt, double wheel_torque_nm);
+
+    double speed_mps() const;
+    double wheel_rpm() const;
+
+private:
+    double m_speed_mps = 0.0;
+
+    static constexpr double kMassKg = 1400.0;
+    static constexpr double kWheelRadiusM = 0.32;
+    static constexpr double kDragCoeff = 0.35; // simplified quadratic drag term
+};