Split the checker engine from its word lists: ca/es catalogs now
live in scripts/check-translations/words.<locale>.txt and all
messages are in English. Adds an es seed (calibrated to zero
errors) and fixes 7 typos it found in es.po. Universal checks
(placeholders, plurals, punctuation) run without a catalog.
AI-assisted-by: muse-spark-1.3-contributor