Replace localeCompare (default-locale, non-deterministic across environments —
unsafe for a persisted sorted index) with UTF-8 byte / code-point order via a
shared compareCodePoints() helper. String ordering is now deterministic and
byte-identical to the native column store / aggregation sort, so results are the
same with or without the native accelerator. Covers the aggregate orderBy sort
and all 5 column-store comparison sites (tail buffer, merge sort, binary search).
Adds compareCodePoints unit tests.
