Update BOT_SETUP.md with full retro mode combo reference, scoring,
and strategy tips. Add docs/bot-guide.md as a standalone developer
guide covering all challenge types including retro mode. Add
docs/sprite-guide.md and sprite-reference.html for custom sprite
creation. Update docs.ts API endpoint and Python example bot with
retro_mode handling.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
