command system
==============

commands are registered as CommandDefinition objects with metadata.

    from mudlib.commands import CommandDefinition, register

    async def my_command(player: Player, args: str) -> None:
        player.writer.write("hello\r\n")
        await player.writer.drain()

    register(CommandDefinition("mycommand", my_command, aliases=["mc"]))

CommandDefinition fields:

    name        primary command name
    handler     async function(player, args)
    aliases     alternative names (default: [])
    mode        required player mode (default: "normal", "*" = any mode)
    help        help text (default: "")

dispatch parses input, looks up the definition, calls its handler:

    await dispatch(player, "mycommand some args")

if the command isn't found, the player gets "Unknown command: ..."

movement
--------

8 directions, each with short and long aliases:

    n/north     s/south     e/east      w/west
    ne/northeast  nw/northwest  se/southeast  sw/southwest

movement checks passability before updating position. impassable terrain
gives "You can't go that way."

nearby players see arrival/departure messages:

    jared leaves east.
    jared arrives from the west.

"nearby" = within viewport range (10 tiles) of old or new position.

look
----

look/l renders the viewport. player is always @ at center. other players
show as *. output is ANSI-colored.

adding commands
---------------

1. create src/mudlib/commands/yourcommand.py
2. import CommandDefinition and register from mudlib.commands
3. define async handler(player, args)
4. call register(CommandDefinition(...))
5. import the module in server.py so registration runs at startup

code
----

src/mudlib/commands/__init__.py    registry + dispatch + CommandDefinition
src/mudlib/commands/movement.py    direction commands
src/mudlib/commands/look.py        look/l
src/mudlib/commands/fly.py         fly
src/mudlib/commands/quit.py        quit/q (mode="*")
src/mudlib/player.py               Player dataclass + registry