Zero-Allocation Text Handling on the Keystroke Path

How I removed 77% of heap allocations from Qwave's omnibox keystroke path — not with unsafe Swift, but by stopping pointless work: a bounded top-6 replacing a full sort of 500, Substring prefix drops replacing replacingOccurrences, and a SQLite prepared-statement cache. 4,370 → 1,011 mallocs per keystroke, all measured and commit-pinned.