Introduces AsyncPlugin to serve as a standalone library-plugin entry point for the Async library. This allows other plugins to depend on Async without bundling it directly. The plugin installs a disconnect hook on start and ensures proper shutdown of tracked scopes.
The only module that imports com.hypixel.*. Provides World.asExecutor,
EntityHandle adapters for Ref/PlayerRef/Player, scope helpers
(playerScope, worldScope, pluginScope), and installAsync() which wires
PlayerDisconnectEvent to PlayerScopes.cancel.