Three more general statements say every card comes from a published site, omitting CultureMech's README

[realmarcin]

Found in the verification review of e115229 on #120, after #208. Still blanket: _fleet/README.md ('Card figures follow the published sites'), the check_cards.py module docstring ('hand-curated from each Mech's published browser'), and assemble_page.py's fleet_records docstring ('the cards cite each Mech's published browser'). The review skill's exception also says 'card figure' though the MECHS entry carries the same README-derived number. Fix: add the CultureMech README exception to each.