Registers a view model instance with the registry.
The key identifying the view model
The view model instance to register
Retrieves a registered view model by key.
The key identifying the view model
The registered view model instance
Clears all registered view model references. Note: This does NOT dispose individual view models -- the Controller is responsible for disposing each view model before calling this.
Registry for managing and accessing view models within a single MAIDR plot instance. Each Controller owns its own ViewModelRegistry for state isolation.