Read the active index under the player lock and remove stale entries
only when the indexed instance id still matches, preventing concurrent
get/complete/reissue from dropping a newer active pointer.
Nest player and instance locks in TryCreateActive, TryMarkComplete, and
TryClearInstance so concurrent create and complete cannot leave a stale
active index or mismatched snapshot.
Ensure instance schema before outcome DDL, require matching player/instance
on Postgres append, catch unique violations on concurrent duplicates, and
add parity plus concurrency integration tests.
Durable per-player contract instances (one active) and append-only
outcome audit rows, mirroring NEO-116/135 store patterns with V011/V012
migrations, AAA tests, README docs, and Bruno health smoke.