Align remaining docs with v3 corrections — errata for position-biased L2 ratios, H100 table fix (MK, powered by Claude)

v3: fix pre-Hopper (32MiB, L2] launch cliff (independently reported); retract position-biased 4090 claims; buffer-fair dtype benchmarks (MK, powered by Claude)

v2: H100 (sm_90) retune — Hopper sub-16MB launch branch, H100 benchmarks/docs, version bump (MK, powered by Claude)