Parse MTTS from telnetlib3 writer during connection and store capabilities
on Player.caps field. Add convenience property Player.color_depth that
delegates to caps.color_depth for easy access by rendering code.
Changes:
- Add caps field to Player with default 16-color ANSI capabilities
- Parse MTTS in server shell after Player creation using parse_mtts()
- Add Player.color_depth property for quick capability checks
- Add tests verifying Player caps integration and color_depth property
