Thank you for the detailed feedback, it's genuinely valuable.
You're right on all technical points : PHPUnit missing from dev dependencies is an oversight I'll fix, and the Unicode limitations are real and should be clearly documented. The NFD/NFKD case is a good catch.
On the use case: fair point. My motivation came from testing MySQL and SQLite full-text search on a shared OVH hosting : the performance with filters was consistently disappointing. That's the itch this scratches. I understand it doesn't match your experience, and that's perfectly legitimate.
Do you have comparative benchmarks on the filter performance? I'm particularly interested in the SQLite FTS case.