The slug transform lives in @arraypress/slug already, with the
unique-against-a-store helpers layered on top. Keeping a second copy
here was drift waiting to happen (accent handling + Unicode decomposition
are tricky enough to want one canonical implementation).

BREAKING: consumers importing `slugify` from `@arraypress/text` should
switch to `@arraypress/slug`.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>