Enable clippy::all, pedantic, nursery, and cargo lint groups at the
workspace level. Fix all resulting warnings: merge identical match arms,
add #[must_use] and doc sections, derive Eq, use clone_from, add type
alias for complex types, extract helpers to reduce function length, and
add crate metadata.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
