docs: add Motorcade wiki Replaces the welcome page with the player guide: the build loop from table to assembler to crowbar, every frame, wheel and engine with the stats each combination produces, the front and rear attachments, driving with drift/turbo/burnout, the road blocks, and the in-game guide book. Documents that there is no fuel system, that driving is client authoritative and therefore exploitable, and that there is no recipe-viewer integration. Co-Authored-By: Claude <noreply@anthropic.com>