Add rust-toolchain.toml so all developers and CI use the same Rust
channel (latest stable = 1.95.0 as of 2026-04-14). Set rust-version
= "1.95" in workspace Cargo.toml to declare the minimum supported
Rust version explicitly.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
funman300