This branch makes existing C++20 tests compile without compiler-specific extensions.
It replaces test-local constexpr expressions involving std::sqrt with const;
the represented scale formula and oracle checks are unchanged.
It also includes <array> directly where tests use std::array deduction.
No production kernel, runtime option or numerical tolerance is changed.
Configure with BUILD_TESTING=ON, build with cmake --build build -j,
and run the affected attention, GDN replay and KV-cache tests with CTest.
This is a test portability prerequisite, not the complete Windows platform port.
See the test guide and build contract.