App-wide configuration cascade for the breadcrumb family. Resolves in
priority order:
Per-instance Input binding.
provideBreadcrumbConfigAt(...) in a parent component's viewProviders.
provideBreadcrumbConfig(...) at the application root.
Library defaults (this token's factory).
providedIn: 'root' with a default factory means consumers never need to
provide the token explicitly - inject(CNGX_BREADCRUMB_CONFIG) always
resolves. Consumers who want overrides call provideBreadcrumbConfig(...)
in bootstrapApplication providers (root cascade) or
provideBreadcrumbConfigAt(...) in a component's viewProviders
(sub-tree cascade).