Implements FTS5-style INSERT INTO v(v) VALUES ('optimize') command that
packs live entries from newer/sparser chunks into free slots of older
chunks, then deletes emptied chunks. Adds hidden command column to vtab
schema, command dispatcher in xUpdate, and two-pointer compaction
algorithm that handles vectors, all metadata types, and partitioned tables.
Includes 16 Python tests, 7 C unit tests, and a libFuzzer target.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
