[Feature] Event/signal system for cross-command communication

[dpid]

Description

Commands currently can't communicate with each other except through shared state. Games often need:

• Fire-and-forget events ("enemy died", "player hit")
• Commands that wait for specific events
• Broadcasting state changes across the command tree

Suggested API

// WaitForEvent command
WaitForEvent.create('enemyDied');

// Fire events from commands
this.emit('damageDealt', { amount: 50 });

// Or at the player/enumerator level
commandPlayer.on('damageDealt', handler);
commandPlayer.emit('damageDealt', data);

Additional Context

Without this, developers end up passing callback functions through constructors or using external event buses. A built-in solution would reduce boilerplate for common game patterns like "play death animation when health reaches zero".