Clippy 1.99.0 added `chunks_exact_to_as_chunks`, which fails `cargo xtask ci`
at its clippy step. Eight uses of `chunks_exact(_mut)` with a constant size now
use `as_chunks(_mut)` (stable since 1.88, within the 1.95 minimum): four in
crates/affinity, three in crates/effects and crates/engine tests, and two in
xtask's sha256. docs/development.md says the gate targets the current stable.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>