Align transient-slip initialization with its dynamics

[rhorvath02]

Summary

• initialize longitudinal and lateral relaxation states with the same smooth effective speed used by their differential equations
• assert zero initial dynamic residual for mirrored forward and reverse cases
• refresh the affected initialization and physical baselines

Why

The prior initial equations used max(abs(Vx), V_min), while the dynamics used sqrt(Vx^2 + V_min^2). Around the low-speed regularization region, that could start the tire relaxation states away from equilibrium.

Validation

• focused OpenModelica physical and initialization checks: 2 passed
• Ruff: passed
• Python/non-OpenModelica suite: 30 passed, 107 skipped because OpenModelica was intentionally omitted from that fast pass