-- pg_turbovec v2.15.0
--
-- MINOR: fixes four open GitHub issues, all additive. No SQL-surface change,
-- no GUC change, no wire-format change (MetaPageData::version stays 8),
-- scoring bit-identical. No REINDEX required.
--
--   #1  An IVF index built on an empty table (or reloaded after TRUNCATE) is
--       now reported as degraded: the empty build stamps `ivf_degraded` and
--       preserves the requested `lists`, so `turbovec.index_is_degraded()`
--       returns true, `turbovec.index_degradation()` reports lists (not 0),
--       and the scan-time WARNING fires. Also fixes a latent crash
--       ("rotation dim must be a positive multiple of 8") on scanning an
--       empty-then-loaded IVF index whose column dim was never pinned.
--   #2  A query vector that arrives as an on-disk TOAST pointer is now
--       detoasted once per scan rather than re-fetched per candidate row
--       (same decoded bytes, results bit-identical).
--   #8  The IVF block-Hadamard rotation matrix (a pure function of dim) is
--       memoized per backend instead of rebuilt per query (bit-identical).
--
-- The empty-IVF reporting fix changes only two scalar fields written at build
-- time; both binaries read each other's empty indexes. To get the degraded
-- report on an already-empty-built index, REINDEX it (optional; reporting
-- only, not correctness). `ALTER EXTENSION pg_turbovec UPDATE TO '2.15.0'` is
-- sufficient. Intentionally empty apart from this comment.