refactor-pipeline

Runs a huge, mechanical refactor (crate or package splits, module extraction, API migrations, dead-code removal) as three independent lanes, producer, packager and shepherd, that coordinate only through git and a PR stack. It pushes branches and opens PRs, so it runs only on /lever refactor or an explicit ask ("split this crate", "break up this monolith", "this module is huge, cut it down", "migrate every caller").