The library reports an absolute maximum compression level of 22, but the CLI
advertises levels 1 through 19 unless `--ultra` is selected. The Rust frontend
used the absolute maximum for both help lines, diverging from the original C
contract and failing the help golden test. Separate the normal help ceiling
from the ultra ceiling and add a focused regression assertion.
Test Plan:
- `cargo fmt --manifest-path rust/cli/Cargo.toml -- --check` -- passed
- `cargo clippy --manifest-path rust/cli/Cargo.toml --lib -- -D warnings` -- passed
- CLI Rust tests -- 162 passed
- `make -C tests -j2 test-cli-tests` -- all 41 passed
- `git diff --check` -- passed
ddidderr
4c94c644c4