AuraLifecycle

Drives the mount lifecycle of a component's AI aura so it animates <em>out</em> as well as in. Without this, dropping AiState to None yanks the <c>.ai-aura-*</c> elements from the DOM instantly and the border/glow flicker away (violating the enter-and-exit rule). A host composes one instance, calls Task}) from <c>OnParametersSet</c>, and renders the aura while Present is true — adding the <c>ai-aura--out</c> class while Exiting so CSS can dissolve it over one <c>--dur-slow</c> beat.