docs: rewrite README for players and administrators

[twme-ai]

Summary

• rewrite the README around user goals instead of release history
• add a dedicated Player Guide covering setup, controls, modes, and commands
• add a dedicated Administrator Guide covering installation, permissions, configuration, localization, integrations, troubleshooting, and compatibility
• retain the existing mode screenshots while moving development details to the end

Validation

• checked all documented commands and behavior against the implementation
• checked every declared permission and top-level config section for README coverage
• rendered the document with GitHub GFM (7 tables rendered)
• verified all Markdown links
• ran Markdown lint with line-length disabled for tables and long URLs
• ran spelling, ASCII, and git diff --check checks