docs(simd): per-CPU dispatch matrix + Codex review fixes #394

Job	Run time
tier4-avx512-check	27s
hpc-stream-parallel/rayon	1m 22s
Pass MSRV values to other jobs	3s
nostd/thumbv6m-none-eabi/stable	27s
format/stable	22s
clippy/1.95.0	40s
native-backend/stable	7m 47s
docs/nightly	-1s
miri	-1s
nightly-simd-polyfill	-1s
cargo-careful	-1s
cross_test/${{ matrix.target }}/${{ matrix.rust }}	-1s
blas-msrv	50s
tests/stable	10m 30s
tests/1.95.0	11m 16s
tests/beta	10m 42s
conclusion	0s
	44m 21s

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