A concrete `LoopStream` resource has a closed typed capability containing:

* a non-empty set of scalar signless integer widths;
* exactly one fixed `dataflow::StreamStepKind`;
* a non-empty set of supported `mlir::arith::CmpIPredicate` values;
* exact physical operand and result roles; and
* its resource-state, use-pattern, holding, timing, and progress contract.