Convenience accessor for the toc configuration cascade. Runs in injection
context; resolves through the priority chain (per-instance Input ->
provideTocConfigAt -> provideTocConfig -> library defaults). Equivalent
to inject(CNGX_TOC_CONFIG) - the helper exists so consumers don't import
the token directly. Mirrors injectBreadcrumbConfig.
export class CngxToc { private readonly cfg = injectTocConfig(); protected readonly navLabel = computed(() => this.cfg.ariaLabels?.nav ?? 'On this page');}