-- 2.0.0 — MAJOR: adopt upstream turbovec 1.0.0. Wire format v7 -> v8
-- (turbovec 1.0.0's TQ+ per-coordinate calibration + v5 block-Hadamard
-- rotation changed the encoded bytes; the QR rotation is gone). This is a
-- BREAKING on-disk change: a pre-v8 (v1..v7) index is detected by
-- MetaPageData::is_legacy_v7() and ambeginscan ERRORs with a
-- `REINDEX INDEX <name>;` hint at first scan (never silent misread). The
-- migration is REINDEX-from-heap: an in-place converter was measured too
-- lossy (double-quantization -20pp R@10 at 4-bit, catastrophic at 2-bit),
-- so the index is rebuilt from the heap's source vectors (full recall).
-- No SQL surface change. This migration is intentionally empty; the format
-- change lives entirely in the extension binary + is handled by REINDEX.