The Double code table's attribution pointed its licence file at the
table's own source. `cargo xtask license-check` requires every asset's
licence file to be a LICENSES.toml document, so the gate failed.
Add prc-rs's LICENSE at the same commit as `licenses/prc-rs-LICENSE.txt`,
fetched unchanged, with its origin and hash in LICENSES.toml, and point
the attribution entry at it. The MIT notice stays in the table's header.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SqmHYx8FiWM5PcsoiErgp9