The AVX half implementation is incomplete, causing the `packetmath_13` test to fail. This disables the test. Also refactored the existing AVX implementation to use `bit_cast` instead of direct access to `.x`.
The AVX half implementation is incomplete, causing the `packetmath_13` test to fail. This disables the test. Also refactored the existing AVX implementation to use `bit_cast` instead of direct access to `.x`.