safe_int, constrained, their error policies, and the safe_iN aliases are
non-framework add-ons, so their public names move out of mp_units into the
mp_units::utility extension tier (next to the representation concepts already
there). The headers move to core/include/mp-units/utility/ accordingly but stay
in the core component: safe_int reuses the core 128-bit integer toolkit
(integral, is_signed_v, int128_t, ...) that also backs the scaling engine, so it
bridges to mp_units::detail with a single using-directive rather than relocating
or duplicating that toolkit. overflow_policies stays framework (it backs bounded
quantity point origins). No deprecation shims: these types are unreleased.
Also fixes utility/representation.h, whose public concepts delegated via the
unqualified detail::X. That resolved to mp_units::detail only as long as
mp_units::utility::detail did not exist; now that constrained/safe_int introduce
it, the references are qualified to ::mp_units::detail:: so they stay
order-independent (this surfaced only in the module build).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>