Update dependencies and Rust

[stepchowfun]

This updates the pinned Rust toolchain and refreshes the lockfile:

• Rust: 1.98.1 → 1.99.0 (and the nightly used for Rustfmt: 2026-09-16 → 2026-10-01). Formatting with the new nightly produced no changes.
• Cargo.lock: transitive updates only (e.g., cc 1.4.7 → 1.5.1, thiserror 2.0.20 → 2.0.21, wasm-bindgen 0.2.128 → 0.2.129, zerocopy 0.8.57 → 0.8.59). All direct dependencies were already at their latest versions.

The copyright year in LICENSE.md is already current, and all GitHub Actions are already at their latest versions.

Status: Ready