feat(test): make integration-go — ephemeral Postgres + generated DSN Add scripts/run-integration-tests.sh: docker run pgvector, dynamic localhost port, TEST_PG_DSN + TEST_PG_RESET_SCHEMA, then go test -tags=integration. Developers are not testing the DSN; this automates disposable infra like CI. Document in BUILD.md and README; keep manual TEST_PG_DSN targets for custom DBs. Made-with: Cursor