FallbackReason

FallbackReason = "not_registered" | "load_failed" | "unresolvable" | "depth_exceeded" | "adapter_requires_server_resolve" | "resolve_failed" | "client_resolve_unsupported" | "reference_needs_renderer"

Why a Presentation could not be handed to a renderer. Closed set — each has a remedy the default panel shows, and a consumer replacing the panel gets the same props.