Add turbocharged twin scenario and cross-platform test harness

verification/B205_BASELINE.md

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+# Saab B205 / 9-5 wagon baseline
+
+Linux Release, 2026-10-23. This quick preset reuses the four-stroke scenario,
+ECU, compressible pipes/volumes, vehicle coupling, spatial audio and dyno.
+The original twin remains available through its backward-compatible type alias.
+There are four actual cylinders and ten pipes, not copies of an audio waveform.
+
+## References and assumptions
+
+[Saab WIS B205 general data](https://saabwisonline.com/9-3-9400/2001/2-engine/basic-engine-4-cylinder-petrol/technical-data/general-data)
+supplies 90 mm bore, 78 mm stroke, approximately 1985 cc, 8.8:1 compression,
+four valves per cylinder and 1-3-4-2 firing order. Cylinder phases in physical
+1/2/3/4 order are 0/180/540/360 degrees; pistons 1/4 move together and 2/3 move
+together. Phased cylinders initialize at their actual piston positions.
+
+[Saab WIS 9-5 gearbox data](https://saabwisonline.com/9-5-9600/2005/4-transmission/manual-gearbox/technical-data/gear-ratio)
+supplies FM55 B05 overall reductions 13.70, 7.12, 4.77, 3.62 and 2.67 with
+4.05 final reduction. The vehicle configuration factors out final reduction
+and has five selectable forward gears, no motorcycle primary reduction.
+
+Other settings are estimates: 1600 kg wagon + 75 kg driver, .317 m loaded tire
+radius, Cd .32, frontal area 2.2 square metres, wheel-equivalent rotational
+inertia 3.6 kg m^2, 300 Nm clutch capacity, crank inertia .18 kg m^2, and
+12 Nm constant + .012 Nm/(rad/s) viscous friction. Road rolling resistance
+retains the shared .015 coefficient. No attempt is made to identify a particular
+year/trim with these estimates.
+
+The intake uses a 3 litre plenum, estimated 52 mm throttle, four 32 mm x 250 mm
+runners, 34 mm x 280 mm headers, .6 litre collector, and a 60 mm x 1.4 m open
+tailpipe. Estimated valves are 32/28 mm intake/exhaust, 8.5/8 mm lift, two each.
+Cams/combustion retain the shared four-stroke model. The ideal ECU targets
+850 RPM idle, with estimated 6500/6250 RPM cut/resume and 2000/1300 overrun
+thresholds. These are scenario calibrations, not a factory Trionic map.
+
+There is no compressor, turbine, intercooler, wastegate, catalyst or muffler in
+this first version. Intake boundary pressure is ambient. Consequently factory
+turbo torque/power and factory exhaust sound are not reproduced. Thermal,
+combustion and single-zone mixing limitations from the fluid audit still apply.
+
+## Verification
+
+The six existing suites passed after the shared four-stroke/vehicle changes.
+The added B205 regression passed independently: it checks engine displacement,
+valve count, cylinder positivity, ten-pipe topology, firing order/cadence, wagon
+launch, five-gear selection, final ratio, idle recovery, finite audio and zero
+pipe positivity repairs. A prescribed 2000 RPM dyno counted 33 firings in half a
+second, consistent with two firing events per revolution. The eight-second
+sequence reached 56.57 km/h in first under load, recovered to 1311 RPM after
+three seconds of unloaded release, and peaked at .18645 audio full scale.
+It cost 7.26 wall seconds while another headless run was also active. Idle
+convergence and engine calibration still need refinement; these checks establish
+basic operation, not measured Saab performance. Windows runtime remains untested.
+
+Run `fluidsim_desktop --scenario b205` or select the third startup card.
+Headless CLI and WAV capture also accept `--scenario b205`. The graph reports
+crankshaft power, not power measured at the wheels.