GTAGPT Mobile Demo v3

Open mobile_demo_v3.html on iPhone/Safari.

New in v3:
- Roads are wider: 4-tile roads on a 10-tile city grid.
- Parked cars placed on roads and parking strips.
- Multiple vehicle types: sedan, taxi, police, van, ambulance, bus, motorcycle.
- Each vehicle has different handling, acceleration, max speed, friction, size, and HP.
- Basic collision damage against props and other vehicles.
- Vehicle HP display in HUD.
- Damaged cars flash red and smoke when low HP.
- Pedestrians still collide and raise wanted stars.
- Mobile controls preserved.

Controls:
- Left touch joystick: move / drive
- ENTER: enter / exit nearest car
- BOOST: speed boost while driving
