V23 introduced a JSONB check constraint (chk_annotation_polygon_quad)
requiring polygon arrays to have exactly 4 points. V30 introduced a
partial unique index preventing two concurrent RUNNING training runs.
These are DB-level invariants that unit tests cannot verify — five
Testcontainers tests now assert they are correctly applied by Flyway
and enforced by PostgreSQL.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>