sequent

Update benchmarks: Sequent 100% recall vs Opus 4.6 92.9%, polish frontend and fix README usage

Fix Z3 false positives: add assignment/loop context to index bounds, remove bogus arithmetic None checks, deduplicate symbolic checks

Fix duplicate symbolic checks — deduplicate divisions and array bounds by line

Remove sequent.yml workflow — was referencing deleted requirements.txt

Rewrite README, clean repo structure, improve benchmark numbers