docs(.claude/ATT): add §16 Adoption Tiers + honest caveats #327

Job	Run time
clippy/1.95.0	46s
Pass MSRV values to other jobs	4s
hpc-stream-parallel/rayon	1m 21s
format/stable	20s
miri	39m 9s
docs/nightly	48s
nostd/thumbv6m-none-eabi/stable	26s
cargo-careful	39s
native-backend/stable	8m 25s
cross_test/${{ matrix.target }}/${{ matrix.rust }}	0s
blas-msrv	1m 0s
tests/beta	10m 38s
tests/1.95.0	10m 57s
tests/stable	10m 25s
conclusion	-1s
	1h 24m 57s

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