Feature 108 (US3, FR-009 generic half): a consumer-generic, dependency-free combinator that folds an ordered `Msg` script over a pure `update`, one step per `Msg`, projecting each resulting model into a running accumulator. Generalises a consumer's hand-rolled frame-counted "tour" into a reusable, byte-stable combinator — pair with `SkillSupport.Random` for byte-stable seeded input. No `Controls`/`Color` dependency; sits beside `SkillSupport.Random`.