Harden cleanup and SIMD admission docs #238

Job	Run time
Miri	18m 12s
no_std target build (x86_64-unknown-freebsd)	19s
Format, lint, test, and audit	1m 42s
Platform tests (macos-26)	26s
Platform tests (windows-latest)	40s
Platform tests (macos-15-intel)	2m 19s
no_std target build (wasm32-unknown-unknown)	18s
no_std target build (thumbv7em-none-eabihf)	20s
Platform tests (ubuntu-latest)	26s
Platform tests (macos-latest)	29s
no_std target build (x86_64-unknown-linux-gnu)	20s
Platform tests (macos-15)	26s
no_std target build (aarch64-unknown-linux-gnu)	21s
	26m 18s

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