Getting the bike and rider into proportion

I revisited the scale of the red bike and its rider in the local build. A lower seat, shorter wheelbase, and more natural rider proportions make them fit together better. Suspension, collision, and connected riding poses now follow that revised shape.

Changelog

• The red dirt bike now has realistic proportions, with a lower seat and shorter wheelbase.
• Suspension and collision follow the resized bike, including smoother wheel extension over ledges.
• The rider now fits the bike with natural adult proportions and correctly sized riding gear.
• Elbows flare outward when accelerating while hands stay on the handlebars; resting and walking poses remain connected.