The server never proactively offered GMCP or MSDP to clients, so
telnetlib3 logged "cannot send MSDP without negotiation" every second.
Now the server sends WILL GMCP and WILL MSDP on connection, and
send_msdp_vitals checks negotiation state before attempting to send.
Zones can now define spawn rules in TOML:
- [[spawns]] sections specify mob type, max count, and respawn timer
- SpawnRule dataclass stores configuration
- load_zone() parses spawn rules from TOML
- Added example spawn rules to treehouse zone (squirrel, crow)
This is configuration infrastructure only - actual spawning logic
will be handled by the game loop in a future phase.
