Old check stripped paint/trim by prefix but used wrong tr- prefix
(transmission, not trim), causing false mismatches on known-good packs.
New approach uses an allowlist of shared WERS prefixes to build variant
signatures — paint, trim, and transmission codes fall out naturally.
Restricts comparison to angle-21 base records only per Ben's spec.
Updates ford_bnp.json profile config accordingly and adds 8 unit tests.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>