App-wide configuration cascade for the data-grid-accordion organism. Resolves
in priority order:
Per-instance [skin] Input binding.
provideDataGridAccordionConfigAt(...) in a parent component's
viewProviders.
provideDataGridAccordionConfig(...) at the application root.
Library default (this token's factory).
providedIn: 'root' with a default factory means consumers never need to
provide the token explicitly - inject(CNGX_DATA_GRID_ACCORDION_CONFIG) always
resolves.