Third Hopfield prefix tier for traces with 7+ snapshots. Runtime selector:
len<=4→p3, 5-6→p5, >=7→p7. Bench-validated: zero regressions vs v1.18.0,
composite PASS on all 4 profiles (bit-identical gate results).

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