The repo ships an MIT LICENSE and the README carries an MIT badge, but the
crates themselves declared no license, so `cargo metadata`, packaging and any
downstream mirror saw "license: null". Adds [workspace.package] license = "MIT"
and inherits it in all five members via license.workspace = true. Verified with
cargo metadata: all five now report MIT.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
