Load engines from TOML and improve scenario audio and carb tuning

Migrate 32 engine definitions into validated startup-loaded TOML files and separate configuration and snapshots from scenario assembly. Add camera-based stereo propagation from shared pipe geometry, preserve exhaust character, tune carburetor mixtures and idle, use ignition cuts for carb engines, and support returning to the scenario menu.

Validation: full Windows build and all 14 CTest checks passed.

include/FluidSim/Scenario.hpp

@@ -1,5 +1,7 @@
 #pragma once
 #include "FluidSim/Silencer.hpp"
+#include "FluidSim/EngineConfig.hpp"
+#include "FluidSim/ScenarioSnapshot.hpp"
 #include "FluidSim/Carburetor.hpp"
 #include <string>
 #include "FluidSim/Junction.hpp"
@@ -19,85 +21,24 @@
 #include <vector>
 
 namespace fluidsim::port {
+struct ScenarioExample;
 
-enum class ScenarioKind { Twin, TwoStroke, SaabB205, AmericanV8 };
-enum class FourStrokePreset { Twin, SaabB205, AmericanV8 };
-
-enum class EngineLayout { Inline, V, Boxer };
-struct EngineConfig {
-    int cylinders{}; // zero selects the existing preset
-    EngineLayout layout{EngineLayout::Inline};
-    float bank_angle{60}, bore{.086f}, stroke{.086f}, rod{.145f}, compression{10};
-    float idle_rpm{1000}, rev_limit{7000}, idle_opening{.045f};
-    bool carbureted{};
-    float carb_pilot_scale{1.f};
-    float carb_jet_scale{1.f}; // multiplier on displacement-scaled effective jet diameters
-    std::array<float,12> phase_degrees{}; // used when custom_phases is true
-    bool custom_phases{};
-};
-
-struct V8ExhaustConfig {
-    float primary_length{.75f}, primary_diameter{.038f};
-    bool h_pipe{true};
-    float junction_volume{50e-6f}; // m3, 50 cc per fitting
-};
-
-struct ScenarioSnapshot {
-    std::string example_name;
-    EngineLayout layout{EngineLayout::Inline};
-    float bank_angle{};
-    bool v8_headers{};
-    PipeSolver pipe_solver{PipeSolver::Rusanov};
-    int cylinder_count{2};
-    float rev_limit_rpm{10000};
-    std::array<float, 12> cylinder_angles{};
-    std::array<float, 12> cylinder_pressures{}, piston_fractions{}, intake_areas{}, exhaust_areas{};
-    std::uint64_t solver_substeps{}, boundary_iterations{}, pipe_positivity_repairs{};
-    float rpm{}, speed_kmh{}, kinetic_energy{}, average_power{}, average_torque{};
-    float cylinder_pressure1{}, cylinder_pressure2{};
-    float cylinder_temperature1{}, cylinder_temperature2{};
-    float cylinder_piston_fraction1{}, cylinder_piston_fraction2{};
-    float valve1_intake_area{}, valve1_exhaust_area{}, valve2_intake_area{}, valve2_exhaust_area{};
-    float intake_pressure{}, exhaust_pressure{}, second_bank_pressure{};
-    std::array<float,2> crossover_pressures{};
-    float throttle{}, pedal{}, target_afr{}, clutch{}, intake_flow{}, exhaust_flow{};
-    bool idle_control{}, fuel_cut{}, two_stroke{}, reed_open{};
-    bool racing_exhaust{};
-    bool silencers{}, h_pipe{};
-    ExhaustConfig exhaust_config{};
-    float crankcase_pressure{};
-    OutdoorScene audio_scene{OutdoorScene::Wall};
-    int gear{};
-    bool rev_limit1{}, rev_limit2{};
-    std::array<std::vector<GasState>, 32> pipe_states;
-    std::array<std::vector<float>, 32> pipe_areas, pipe_lengths;
-    void capture_pipes(const std::vector<Pipe1D>& pipes) {
-        for (std::size_t k = 0; k < pipes.size(); ++k) {
-            pipe_positivity_repairs += pipes[k].positivity_repairs;
-            pipe_areas[k] = pipes[k].cell_areas;
-            pipe_lengths[k] = pipes[k].cell_lengths;
-            pipe_states[k].reserve(pipes[k].cells.size());
-            for (std::size_t i = 0; i < pipes[k].cells.size(); ++i)
-                pipe_states[k].push_back(pipes[k].state(static_cast<int>(i)));
-        }
-    }
-};
-
-// Shared four-stroke topology: independent runners/headers and shared plenums.
-// Presets include a 600 cc twin, B205-sized inline-four and American 5.0 V8.
+// Calibrated four-stroke assembly with independent runners and shared plenums.
 class FourStrokeScenario : public MotorcycleTest {
 public:
-    explicit FourStrokeScenario(int sample_rate = 44100, FourStrokePreset preset = FourStrokePreset::Twin, ExhaustConfig exhaust = {}, V8ExhaustConfig v8_exhaust = {}, EngineConfig engine = {});
-    const FourStrokePreset preset;
+    explicit FourStrokeScenario(int sample_rate = 44100, FourStrokePreset preset = FourStrokePreset::Twin);
+    FourStrokeScenario(int sample_rate, const ScenarioExample& definition);
+    FourStrokeScenario(int sample_rate, EngineConfig engine, ExhaustConfig exhaust = {}, JunctionConfig junctions = {});
     const ExhaustConfig exhaust_config;
-    const V8ExhaustConfig v8_exhaust_config;
+    const JunctionConfig junction_config;
     const EngineConfig engine_config;
-    int cylinder_count() const { return engine_config.cylinders ? engine_config.cylinders : preset == FourStrokePreset::AmericanV8 ? 8 : preset == FourStrokePreset::SaabB205 ? 4 : 2; }
+    int cylinder_count() const { return engine_config.cylinders; }
     std::array<FourStrokeCylinder*, 12> cylinders() { return {&cylinder1, &cylinder2, &cylinder3, &cylinder4,
         &cylinder5, &cylinder6, &cylinder7, &cylinder8,&cylinder9,&cylinder10,&cylinder11,&cylinder12}; }
     AudioFrame process();
     void set_controls(float throttle_value, float load_value, float clutch_value);
     void set_audio_scene(OutdoorScene scene);
+    void set_listener(AudioListener listener);
     void set_pipe_solver(PipeSolver solver);
     void set_monitor_filter(bool enabled);
     void set_starter(bool engaged);
@@ -115,8 +56,8 @@ public:
     FourStrokeCylinder cylinder1{}, cylinder2{}, cylinder3{}, cylinder4{};
     FourStrokeCylinder cylinder5{}, cylinder6{}, cylinder7{}, cylinder8{};
     FourStrokeCylinder cylinder9{}, cylinder10{}, cylinder11{}, cylinder12{};
-    Volume0D intake_plenum{1.0e-3f, 101325.0f, 300.0f};
-    Junction exhaust_collector{0.15e-3f, 101325.0f, 700.0f};
+    Volume0D intake_plenum;
+    Junction exhaust_collector;
     std::vector<Pipe1D> pipes;
     float intake_flow{}, exhaust_flow{};
     std::uint64_t sample_count{};
@@ -134,7 +75,7 @@ private:
     Port* throttle_port_{};
 
     static float area_for_diameter(float diameter);
-    static std::vector<Pipe1D> create_pipes(FourStrokePreset preset, const ExhaustConfig& exhaust, const V8ExhaustConfig& v8_exhaust, const EngineConfig& engine);
+    static std::vector<Pipe1D> create_pipes(const EngineConfig& engine, const ExhaustConfig& exhaust);
 };
 
 using FourStrokeTwinScenario = FourStrokeScenario;