Implements import_map.py script that converts YAML zone definitions to
TOML format used by the engine. YAML format supports all zone features
including terrain, portals, spawns, ambient messages, and boundaries.
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
