Add turbocharged twin scenario and cross-platform test harness

include/FluidSim/Vehicle.hpp

@@ -1,14 +1,14 @@
 #pragma once
 
-#include <array>
+#include <vector>
 
 namespace fluidsim::port {
 
-// Longitudinal motorcycle model and the friction clutch coupling it to the crank.
+// Longitudinal vehicle model and the friction clutch coupling it to the crank.
 class Vehicle {
 public:
     int current_gear{};
-    std::array<float, 6> gear_ratios{4.1f, 2.7f, 2.0f, 1.55f, 1.25f, 0.98f};
+    std::vector<float> gear_ratios{4.1f, 2.7f, 2.0f, 1.55f, 1.25f, 0.98f};
     float final_drive_ratio{2.7f}, primary_reduction{1.8f};
     float clutch_input{1.0f}, clutch_capacity{80.0f}, clutch_engagement_rate{8.0f};
     float mass{160.0f}, wheel_radius{0.32f}, rotational_inertia{1.2f};