Convenience accessor for the data-grid-accordion configuration cascade. Runs in
injection context; resolves through the priority chain (per-instance Input
-> provideDataGridAccordionConfigAt -> provideDataGridAccordionConfig ->
library defaults). Equivalent to inject(CNGX_DATA_GRID_ACCORDION_CONFIG) -
the helper exists so consumers don't import the token directly. Mirrors
injectAccordionConfig in @cngx/ui/accordion.