Add a Set predicate for bundled or derived paths #8

Add a Set predicate for "bundled or derived" — Has(Vendor) || Has(Fixture) || Has(Cache) || Has(BuildOutput). The four compositions in the README all need that filter and will each hand-roll it.

Also worth stating in the README that a role set cannot answer "is this first-party code". scripts/deploy.py is tooling with no source, so a consumer filtering on Source drops it. The existing note that source "describes layout" reads as a caveat about source rather than about the absence of layout roles.

Found in git-pkgs/brief#202, which derived its own predicate and included Test and Tooling in the exclusions. A tree of scripts/deploy.py plus alembic.ini went from reporting Python and Alembic to reporting nothing.