contains? did not support dict key membership in the real runtime —
(contains? {:a 1} :a) threw "contains?: 2 args", contradicting its own :doc.
The fix landed (primitives.sx + sx_primitives.ml) but had no pinning test.
Add suite gate-K20-contains-dict to spec/tests/test-gate-pins.sx (4 tests,
repro from plans/sx-review/core.md): present key true, missing key false,
list membership + string substring unchanged. 8/8 green under OCaml run_tests.
Test-only: no semantics edits, no push.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
giles
0ceb9d1776