GTAGPT Mobile Demo

Open mobile_demo.html on iPhone/Safari.

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

This is an iPhone-friendly vertical slice with:
- full-screen canvas
- safe-area aware HUD
- touch joystick
- action buttons
- camera follow
- procedural roads
- pedestrians
- vehicle enter/exit
- wanted stars
