Element-injector twin of provideDirection. Returns Provider[]
so it can go in a component's viewProviders (or providers) array,
forcing the direction injectDirection reports for that DI subtree
without touching documentElement.dir. Reach for it when a composite's
keyboard-nav logic must honour a forced subtree direction; the
environment-scoped provideDirection returns EnvironmentProviders,
which an element injector rejects.