chore: upgrade Rust toolchain to 1.95.0 (#3390)

Bumps the pinned toolchain in `rust-toolchain.toml` from 1.94.0 to
1.95.0.

Fixes new lints surfaced by clippy on 1.95.0:

- `manual_checked_ops` — fragment size mean in `table.rs` uses
`checked_div`
- `explicit_counter_loop` — shuffle test loop in `shuffle.rs`

No rustc warnings were introduced.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>