New Vector type (value array) with 11 primitives: - make-vector, vector — constructors - vector-ref, vector-set! — element access/mutation - vector-length, vector?, vector-fill! — inspection - vector->list, list->vector — conversion - vector-copy — independent copy - Element-wise equality in safe_eq 10 new tests (2668/2668 pass). Follows Record pattern (value array). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>