[rhorvath02]

Purpose

Make halfshafts and differential behavior independently usable components of the driveline.

Approach

Add an explicit halfshaft model, an ideal open differential, and categorical drive-layout/differential selections. Keep these components separate from the vehicle-level driveline adapter.

Validation

Includes halfshaft, open-differential and locked-differential fixtures. Fixture paths, test collection and Modelica formatting checked.

[raorjun]

The non-spatial halfshaft reaction path still assumes the old wheel. With the #43 wheel, it puts a spin-axis moment on the upright that should not be there.

[raorjun]

Fixed in c06d968. Halfshaft now rejects useWheelFrame = true with useMount = false when world.driveTrainMechanics3D = true, with the message "Halfshaft: useWheelFrame with a 3D drivetrain requires useMount". The guard is in Halfshaft, not InboardShaft, because BrakeReactionSmoke uses the non-spatial shaft on purpose. The InboardShaft docs no longer say the contact moment enters the upright. TestHalfshaft, the differential fixtures and BrakeReactionSmoke simulate. VehicleSim, VehicleFMI and TestRearFinalDriveDifferential pass at the tip. A fixture with the bad combination fails with the message.

[raorjun]

Approve. CI is green, and the review findings are fixed or addressed in the comments above.