P3.9 chassis and airflow development after the frozen P3.8 release.

New work: finite-rate collective upper-vent angle study, front-projection active
camber, tyre/joint material requirements, wider wheel-motion packaging and
rerouted ducts. Original vehicle benchmarks and published P3.7/P3.8 source
archives remain frozen. New computational results are separated from physical
validation, tyre-force benefits and unqualified new-body CFD.

The initial travel mesh repair attempts are retained as history. The complete
OpenFOAM gates still apply before any flow solve. Physical measurements: 0.
