Replace the concrete ResourceName(String) with a type parameter
R: Clone + Eq + Hash threaded end-to-end (Dep<R>, Node<N,R>, Graph<N,R>,
ResourceTable<R>, ResourceGuard<R>/SharedResources<R>, Scheduler<N,R>).
The crate no longer hard-codes the resource identity; the consumer picks
the concrete type (a String, or an enum like BuildSlot/Agent(name)) at
the port. Tests use String as the concrete R. Pure type-parameter
thread-through, no logic change. 25 tests green, clippy pedantic clean.
