[rubentalstra]

What changed and why

The FerroHEALTH family builds with the latest stable toolchain, Rust 1.99.1 (released 2026-10-15), and declares the release before it as its MSRV (owner decision 2026-10-21). This workspace already declares rust-version = "1.98", so only the toolchain moves.

• rust-toolchain.toml and the docs/VERSIONS.md row move from 1.98.1 to 1.99.1.
• Clippy 1.99 adds the pedantic assert_is_empty lint. Its seven sites, all under tests/, now use assert_eq! or assert_ne! against an empty value of the same type, so a failure prints the value. No file a published crate packages changes, so neither crate version moves.

Licensing of contributions

• I accept the terms in CONTRIBUTING.md § Licensing of contributions: I have the right to submit this work, I license it under the project licence of the version it lands in, and I grant the Licensor the relicensing right stated there.

Checklist

• Rust gates pass: cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings with and without --all-features and for every feature set of the CI matrix, cargo nextest run --workspace --locked with and without --all-features, the doctests, cargo doc with RUSTDOCFLAGS=-D warnings; versions.sh, comment-style.sh and crate-version-guard.sh pass.
• No test was weakened: each rewritten assertion checks the same condition.
• CHANGELOG.md has an [Unreleased] entry.
• No patient data, real identifier, key, token or password in a fixture, test or example.
• Every commit is signed.
• No AI or assistant attribution anywhere in the commits or this PR.