fix(profile): a clippy 1.98 lint that would have failed CI

`chunks_exact_to_as_chunks` is new in clippy 1.98 and fires on
`read_scheme_name`, in code this batch never touched. CI checks with
`-D warnings` on stable, so this would have gone red on the next run whatever
was committed.

`as_chunks::<2>()` yields `&[u8; 2]` directly, so the two index operations go
away with the lint.

Worth noting for the same reason the handoff already records about MSRV: which
lints run is a property of the toolchain, not of the code. Nothing here changed
and the check went from green to red.

Unverified: `slice::as_chunks` against the declared 1.88 floor. Clippy's lint is
MSRV-gated and fired with `rust-version = "1.88"` in the manifest, which implies
it is available there -- but that is inference, not a build, and this project
has shipped a false floor before. `cargo +1.88 check --all-targets` could not
run here because that toolchain's sysroot is missing its rlibs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>